Fix file corrupted in some cases, check file extension and format code

Fix file corrupted when save as in XLAM / XLSM / XLTM / XLTX extension in some case
New exported error ErrWorkbookExt has been added, and check file extension on save the workbook
Format source code with `gofumpt`

33 files changed, 225 insertions, 150 deletions

diff --git a/.gitignore b/.gitignore
index 68532a7..4dce768 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,9 @@
 ~$*.xlsx
-test/Test*.xlsx
+test/Test*.xlam
 test/Test*.xlsm
+test/Test*.xlsx
+test/Test*.xltm
+test/Test*.xltx
 # generated files
 test/BadEncrypt.xlsx
 test/BadWorkbook.SaveAsEmptyStruct.xlsx
diff --git a/README.md b/README.md
index a0d2d3d..8e16a88 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@
 
 ## Introduction
 
-Excelize is a library written in pure Go providing a set of functions that allow you to write to and read from XLSX / XLSM / XLTM / XLTX files. Supports reading and writing spreadsheet documents generated by Microsoft Excel™ 2007 and later. Supports complex components by high compatibility, and provided streaming API for generating or reading data from a worksheet with huge amounts of data. This library needs Go version 1.15 or later. The full API docs can be seen using go's built-in documentation tool, or online at [go.dev](https://pkg.go.dev/github.com/xuri/excelize/v2) and [docs reference](https://xuri.me/excelize/).
+Excelize is a library written in pure Go providing a set of functions that allow you to write to and read from XLAM / XLSM / XLSX / XLTM / XLTX files. Supports reading and writing spreadsheet documents generated by Microsoft Excel™ 2007 and later. Supports complex components by high compatibility, and provided streaming API for generating or reading data from a worksheet with huge amounts of data. This library needs Go version 1.15 or later. The full API docs can be seen using go's built-in documentation tool, or online at [go.dev](https://pkg.go.dev/github.com/xuri/excelize/v2) and [docs reference](https://xuri.me/excelize/).
 
 ## Basic Usage
 
diff --git a/README_zh.md b/README_zh.md
index 919e954..dafdd93 100644
--- a/README_zh.md
+++ b/README_zh.md
@@ -13,7 +13,7 @@
 
 ## 简介
 
-Excelize 是 Go 语言编写的用于操作 Office Excel 文档基础库，基于 ECMA-376，ISO/IEC 29500 国际标准。可以使用它来读取、写入由 Microsoft Excel™ 2007 及以上版本创建的电子表格文档。支持 XLSX / XLSM / XLTM / XLTX 等多种文档格式，高度兼容带有样式、图片(表)、透视表、切片器等复杂组件的文档，并提供流式读写 API，用于处理包含大规模数据的工作簿。可应用于各类报表平台、云计算、边缘计算等系统。使用本类库要求使用的 Go 语言为 1.15 或更高版本，完整的 API 使用文档请访问 [go.dev](https://pkg.go.dev/github.com/xuri/excelize/v2) 或查看 [参考文档](https://xuri.me/excelize/)。
+Excelize 是 Go 语言编写的用于操作 Office Excel 文档基础库，基于 ECMA-376，ISO/IEC 29500 国际标准。可以使用它来读取、写入由 Microsoft Excel™ 2007 及以上版本创建的电子表格文档。支持 XLAM / XLSM / XLSX / XLTM / XLTX 等多种文档格式，高度兼容带有样式、图片(表)、透视表、切片器等复杂组件的文档，并提供流式读写 API，用于处理包含大规模数据的工作簿。可应用于各类报表平台、云计算、边缘计算等系统。使用本类库要求使用的 Go 语言为 1.15 或更高版本，完整的 API 使用文档请访问 [go.dev](https://pkg.go.dev/github.com/xuri/excelize/v2) 或查看 [参考文档](https://xuri.me/excelize/)。
 
 ## 快速上手
 
diff --git a/adjust_test.go b/adjust_test.go
index b2ec3c4..ab6bedc 100644
--- a/adjust_test.go
+++ b/adjust_test.go
@@ -298,9 +298,11 @@ func TestAdjustHelper(t *testing.T) {
 	f := NewFile()
 	f.NewSheet("Sheet2")
 	f.Sheet.Store("xl/worksheets/sheet1.xml", &xlsxWorksheet{
-		MergeCells: &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A:B1"}}}})
+		MergeCells: &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A:B1"}}},
+	})
 	f.Sheet.Store("xl/worksheets/sheet2.xml", &xlsxWorksheet{
-		AutoFilter: &xlsxAutoFilter{Ref: "A1:B"}})
+		AutoFilter: &xlsxAutoFilter{Ref: "A1:B"},
+	})
 	// testing adjustHelper with illegal cell coordinates.
 	assert.EqualError(t, f.adjustHelper("Sheet1", rows, 0, 0), newCellNameToCoordinatesError("A", newInvalidCellNameError("A")).Error())
 	assert.EqualError(t, f.adjustHelper("Sheet2", rows, 0, 0), newCellNameToCoordinatesError("B", newInvalidCellNameError("B")).Error())
diff --git a/calc.go b/calc.go
index 89eb087..b3c6df8 100644
--- a/calc.go
+++ b/calc.go
@@ -1377,7 +1377,7 @@ func (f *File) rangeResolver(cellRefs, cellRanges *list.List) (arg formulaArg, e
 	if cellRanges.Len() > 0 {
 		arg.Type = ArgMatrix
 		for row := valueRange[0]; row <= valueRange[1]; row++ {
-			var matrixRow = []formulaArg{}
+			matrixRow := []formulaArg{}
 			for col := valueRange[2]; col <= valueRange[3]; col++ {
 				var cell, value string
 				if cell, err = CoordinatesToCellName(col, row); err != nil {
@@ -1473,7 +1473,7 @@ func formulaCriteriaParser(exp string) (fc *formulaCriteria) {
 func formulaCriteriaEval(val string, criteria *formulaCriteria) (result bool, err error) {
 	var value, expected float64
 	var e error
-	var prepareValue = func(val, cond string) (value float64, expected float64, err error) {
+	prepareValue := func(val, cond string) (value float64, expected float64, err error) {
 		if value, err = strconv.ParseFloat(val, 64); err != nil {
 			return
 		}
@@ -3385,7 +3385,7 @@ func (fn *formulaFuncs) DECIMAL(argsList *list.List) formulaArg {
 	if argsList.Len() != 2 {
 		return newErrorFormulaArg(formulaErrorVALUE, "DECIMAL requires 2 numeric arguments")
 	}
-	var text = argsList.Front().Value.(formulaArg).String
+	text := argsList.Front().Value.(formulaArg).String
 	var radix int
 	var err error
 	radix, err = strconv.Atoi(argsList.Back().Value.(formulaArg).String)
@@ -3934,7 +3934,7 @@ func (fn *formulaFuncs) MDETERM(argsList *list.List) (result formulaArg) {
 		return newErrorFormulaArg(formulaErrorVALUE, "MDETERM requires at least 1 argument")
 	}
 	strMtx = argsList.Front().Value.(formulaArg).Matrix
-	var rows = len(strMtx)
+	rows := len(strMtx)
 	for _, row := range argsList.Front().Value.(formulaArg).Matrix {
 		if len(row) != rows {
 			return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
@@ -4257,30 +4257,107 @@ type romanNumerals struct {
 
 var romanTable = [][]romanNumerals{
 	{
-		{1000, "M"}, {900, "CM"}, {500, "D"}, {400, "CD"}, {100, "C"}, {90, "XC"},
-		{50, "L"}, {40, "XL"}, {10, "X"}, {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"},
+		{1000, "M"},
+		{900, "CM"},
+		{500, "D"},
+		{400, "CD"},
+		{100, "C"},
+		{90, "XC"},
+		{50, "L"},
+		{40, "XL"},
+		{10, "X"},
+		{9, "IX"},
+		{5, "V"},
+		{4, "IV"},
+		{1, "I"},
 	},
 	{
-		{1000, "M"}, {950, "LM"}, {900, "CM"}, {500, "D"}, {450, "LD"}, {400, "CD"},
-		{100, "C"}, {95, "VC"}, {90, "XC"}, {50, "L"}, {45, "VL"}, {40, "XL"},
-		{10, "X"}, {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"},
+		{1000, "M"},
+		{950, "LM"},
+		{900, "CM"},
+		{500, "D"},
+		{450, "LD"},
+		{400, "CD"},
+		{100, "C"},
+		{95, "VC"},
+		{90, "XC"},
+		{50, "L"},
+		{45, "VL"},
+		{40, "XL"},
+		{10, "X"},
+		{9, "IX"},
+		{5, "V"},
+		{4, "IV"},
+		{1, "I"},
 	},
 	{
-		{1000, "M"}, {990, "XM"}, {950, "LM"}, {900, "CM"}, {500, "D"}, {490, "XD"},
-		{450, "LD"}, {400, "CD"}, {100, "C"}, {99, "IC"}, {90, "XC"}, {50, "L"},
-		{45, "VL"}, {40, "XL"}, {10, "X"}, {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"},
+		{1000, "M"},
+		{990, "XM"},
+		{950, "LM"},
+		{900, "CM"},
+		{500, "D"},
+		{490, "XD"},
+		{450, "LD"},
+		{400, "CD"},
+		{100, "C"},
+		{99, "IC"},
+		{90, "XC"},
+		{50, "L"},
+		{45, "VL"},
+		{40, "XL"},
+		{10, "X"},
+		{9, "IX"},
+		{5, "V"},
+		{4, "IV"},
+		{1, "I"},
 	},
 	{
-		{1000, "M"}, {995, "VM"}, {990, "XM"}, {950, "LM"}, {900, "CM"}, {500, "D"},
-		{495, "VD"}, {490, "XD"}, {450, "LD"}, {400, "CD"}, {100, "C"}, {99, "IC"},
-		{90, "XC"}, {50, "L"}, {45, "VL"}, {40, "XL"}, {10, "X"}, {9, "IX"},
-		{5, "V"}, {4, "IV"}, {1, "I"},
+		{1000, "M"},
+		{995, "VM"},
+		{990, "XM"},
+		{950, "LM"},
+		{900, "CM"},
+		{500, "D"},
+		{495, "VD"},
+		{490, "XD"},
+		{450, "LD"},
+		{400, "CD"},
+		{100, "C"},
+		{99, "IC"},
+		{90, "XC"},
+		{50, "L"},
+		{45, "VL"},
+		{40, "XL"},
+		{10, "X"},
+		{9, "IX"},
+		{5, "V"},
+		{4, "IV"},
+		{1, "I"},
 	},
 	{
-		{1000, "M"}, {999, "IM"}, {995, "VM"}, {990, "XM"}, {950, "LM"}, {900, "CM"},
-		{500, "D"}, {499, "ID"}, {495, "VD"}, {490, "XD"}, {450, "LD"}, {400, "CD"},
-		{100, "C"}, {99, "IC"}, {90, "XC"}, {50, "L"}, {45, "VL"}, {40, "XL"},
-		{10, "X"}, {9, "IX"}, {5, "V"}, {4, "IV"}, {1, "I"},
+		{1000, "M"},
+		{999, "IM"},
+		{995, "VM"},
+		{990, "XM"},
+		{950, "LM"},
+		{900, "CM"},
+		{500, "D"},
+		{499, "ID"},
+		{495, "VD"},
+		{490, "XD"},
+		{450, "LD"},
+		{400, "CD"},
+		{100, "C"},
+		{99, "IC"},
+		{90, "XC"},
+		{50, "L"},
+		{45, "VL"},
+		{40, "XL"},
+		{10, "X"},
+		{9, "IX"},
+		{5, "V"},
+		{4, "IV"},
+		{1, "I"},
 	},
 }
 
@@ -4751,8 +4828,8 @@ func (fn *formulaFuncs) SUMIF(argsList *list.List) formulaArg {
 	if argsList.Len() < 2 {
 		return newErrorFormulaArg(formulaErrorVALUE, "SUMIF requires at least 2 arguments")
 	}
-	var criteria = formulaCriteriaParser(argsList.Front().Next().Value.(formulaArg).String)
-	var rangeMtx = argsList.Front().Value.(formulaArg).Matrix
+	criteria := formulaCriteriaParser(argsList.Front().Next().Value.(formulaArg).String)
+	rangeMtx := argsList.Front().Value.(formulaArg).Matrix
 	var sumRange [][]formulaArg
 	if argsList.Len() == 3 {
 		sumRange = argsList.Back().Value.(formulaArg).Matrix
@@ -5886,7 +5963,7 @@ func (fn *formulaFuncs) MEDIAN(argsList *list.List) formulaArg {
 	if argsList.Len() == 0 {
 		return newErrorFormulaArg(formulaErrorVALUE, "MEDIAN requires at least 1 argument")
 	}
-	var values = []float64{}
+	values := []float64{}
 	var median, digits float64
 	var err error
 	for token := argsList.Front(); token != nil; token = token.Next() {
@@ -9047,7 +9124,6 @@ func compareFormulaArg(lhs, rhs, matchMode formulaArg, caseSensitive bool) byte
 			if matchPattern(rs, ls) {
 				return criteriaEq
 			}
-
 		}
 		return map[int]byte{1: criteriaG, -1: criteriaL, 0: criteriaEq}[strings.Compare(ls, rs)]
 	case ArgEmpty:
@@ -9931,9 +10007,8 @@ func (fn *formulaFuncs) ACCRINT(argsList *list.List) formulaArg {
 			return newErrorFormulaArg(formulaErrorNUM, formulaErrorNUM)
 		}
 	}
-	cm := newBoolFormulaArg(true)
 	if argsList.Len() == 8 {
-		if cm = argsList.Back().Value.(formulaArg).ToBool(); cm.Type != ArgNumber {
+		if cm := argsList.Back().Value.(formulaArg).ToBool(); cm.Type != ArgNumber {
 			return newErrorFormulaArg(formulaErrorVALUE, formulaErrorVALUE)
 		}
 	}
@@ -10206,10 +10281,8 @@ func coupdays(from, to time.Time, basis int) float64 {
 			date = date.AddDate(0, 13-int(date.Month()), 0)
 		}
 		days += getDaysInMonthRange(toY, int(date.Month()), int(toM)-1, basis)
-		date = date.AddDate(0, int(toM)-int(date.Month()), 0)
 	}
-	days += toDay - fromDay
-	if days > 0 {
+	if days += toDay - fromDay; days > 0 {
 		return float64(days)
 	}
 	return 0
@@ -11375,8 +11448,7 @@ func (fn *formulaFuncs) ODDFPRICE(argsList *list.List) formulaArg {
 	if args.Type != ArgList {
 		return args
 	}
-	settlement, maturity, issue, firstCoupon, rate, yld, redemption, frequency, basisArg :=
-		args.List[0], args.List[1], args.List[2], args.List[3], args.List[4], args.List[5], args.List[6], args.List[7], args.List[8]
+	settlement, maturity, issue, firstCoupon, rate, yld, redemption, frequency, basisArg := args.List[0], args.List[1], args.List[2], args.List[3], args.List[4], args.List[5], args.List[6], args.List[7], args.List[8]
 	if basisArg.Number < 0 || basisArg.Number > 4 {
 		return newErrorFormulaArg(formulaErrorNUM, "invalid basis")
 	}
diff --git a/calc_test.go b/calc_test.go
index a9899d1..c3be308 100644
--- a/calc_test.go
+++ b/calc_test.go
@@ -3386,7 +3386,6 @@ func TestCalcCellValue(t *testing.T) {
 	_, err = f.CalcCellValue("Sheet1", "A1")
 	assert.EqualError(t, err, "not support UNSUPPORT function")
 	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestCalcCellValue.xlsx")))
-
 }
 
 func TestCalculate(t *testing.T) {
@@ -3438,7 +3437,6 @@ func TestCalcWithDefinedName(t *testing.T) {
 	result, err = f.CalcCellValue("Sheet1", "D1")
 	assert.NoError(t, err)
 	assert.Equal(t, "YES", result, `=IF("B1_as_string"=defined_name1,"YES","NO")`)
-
 }
 
 func TestCalcISBLANK(t *testing.T) {
@@ -3748,7 +3746,8 @@ func TestCalcXIRR(t *testing.T) {
 		{25.00, "02/01/2017"},
 		{8.00, "03/01/2017"},
 		{15.00, "06/01/2017"},
-		{-1e-10, "09/01/2017"}}
+		{-1e-10, "09/01/2017"},
+	}
 	f := prepareCalcData(cellData)
 	formulaList := map[string]string{
 		"=XIRR(A1:A4,B1:B4)":     "-0.196743861298328",
@@ -3886,7 +3885,8 @@ func TestCalcXLOOKUP(t *testing.T) {
 }
 
 func TestCalcXNPV(t *testing.T) {
-	cellData := [][]interface{}{{nil, 0.05},
+	cellData := [][]interface{}{
+		{nil, 0.05},
 		{"01/01/2016", -10000, nil},
 		{"02/01/2016", 2000},
 		{"05/01/2016", 2400},
@@ -3895,7 +3895,8 @@ func TestCalcXNPV(t *testing.T) {
 		{"01/01/2017", 4100},
 		{},
 		{"02/01/2016"},
-		{"01/01/2016"}}
+		{"01/01/2016"},
+	}
 	f := prepareCalcData(cellData)
 	formulaList := map[string]string{
 		"=XNPV(B1,B2:B7,A2:A7)": "4447.938009440515",
diff --git a/cell_test.go b/cell_test.go
index 8d00e2d..f6f1098 100644
--- a/cell_test.go
+++ b/cell_test.go
@@ -30,11 +30,13 @@ func TestConcurrency(t *testing.T) {
 			_, err := f.GetCellValue("Sheet1", fmt.Sprintf("A%d", val))
 			assert.NoError(t, err)
 			// Concurrency set rows
-			assert.NoError(t, f.SetSheetRow("Sheet1", "B6", &[]interface{}{" Hello",
+			assert.NoError(t, f.SetSheetRow("Sheet1", "B6", &[]interface{}{
+				" Hello",
 				[]byte("World"), 42, int8(1<<8/2 - 1), int16(1<<16/2 - 1), int32(1<<32/2 - 1),
 				int64(1<<32/2 - 1), float32(42.65418), float64(-42.65418), float32(42), float64(42),
 				uint(1<<32 - 1), uint8(1<<8 - 1), uint16(1<<16 - 1), uint32(1<<32 - 1),
-				uint64(1<<32 - 1), true, complex64(5 + 10i)}))
+				uint64(1<<32 - 1), true, complex64(5 + 10i),
+			}))
 			// Concurrency create style
 			style, err := f.NewStyle(`{"font":{"color":"#1265BE","underline":"single"}}`)
 			assert.NoError(t, err)
@@ -384,7 +386,7 @@ func TestGetCellFormula(t *testing.T) {
 
 func ExampleFile_SetCellFloat() {
 	f := NewFile()
-	var x = 3.14159265
+	x := 3.14159265
 	if err := f.SetCellFloat("Sheet1", "A1", x, 2, 64); err != nil {
 		fmt.Println(err)
 	}
@@ -534,6 +536,7 @@ func TestGetCellRichText(t *testing.T) {
 	_, err = f.GetCellRichText("Sheet1", "A")
 	assert.EqualError(t, err, newCellNameToCoordinatesError("A", newInvalidCellNameError("A")).Error())
 }
+
 func TestSetCellRichText(t *testing.T) {
 	f := NewFile()
 	assert.NoError(t, f.SetRowHeight("Sheet1", 1, 35))
diff --git a/comment.go b/comment.go
index aa066ec..c0dc33b 100644
--- a/comment.go
+++ b/comment.go
@@ -74,7 +74,7 @@ func (f *File) GetComments() (comments map[string][]Comment) {
 // getSheetComments provides the method to get the target comment reference by
 // given worksheet file path.
 func (f *File) getSheetComments(sheetFile string) string {
-	var rels = "xl/worksheets/_rels/" + sheetFile + ".rels"
+	rels := "xl/worksheets/_rels/" + sheetFile + ".rels"
 	if sheetRels := f.relsReader(rels); sheetRels != nil {
 		sheetRels.Lock()
 		defer sheetRels.Unlock()
diff --git a/crypt.go b/crypt.go
index 91beab2..9912a67 100644
--- a/crypt.go
+++ b/crypt.go
@@ -168,16 +168,20 @@ func Encrypt(raw []byte, opt *Options) (packageBuf []byte, err error) {
 			HashAlgorithm:   "SHA512",
 			SaltValue:       base64.StdEncoding.EncodeToString(keyDataSaltValue),
 		},
-		KeyEncryptors: KeyEncryptors{KeyEncryptor: []KeyEncryptor{{
-			EncryptedKey: EncryptedKey{SpinCount: 100000, KeyData: KeyData{
-				CipherAlgorithm: "AES",
-				CipherChaining:  "ChainingModeCBC",
-				HashAlgorithm:   "SHA512",
-				HashSize:        64,
-				BlockSize:       16,
-				KeyBits:         256,
-				SaltValue:       base64.StdEncoding.EncodeToString(keyEncryptors)},
-			}}},
+		KeyEncryptors: KeyEncryptors{
+			KeyEncryptor: []KeyEncryptor{{
+				EncryptedKey: EncryptedKey{
+					SpinCount: 100000, KeyData: KeyData{
+						CipherAlgorithm: "AES",
+						CipherChaining:  "ChainingModeCBC",
+						HashAlgorithm:   "SHA512",
+						HashSize:        64,
+						BlockSize:       16,
+						KeyBits:         256,
+						SaltValue:       base64.StdEncoding.EncodeToString(keyEncryptors),
+					},
+				},
+			}},
 		},
 	}
 
@@ -481,7 +485,7 @@ func convertPasswdToKey(passwd string, blockKey []byte, encryption Encryption) (
 
 // hashing data by specified hash algorithm.
 func hashing(hashAlgorithm string, buffer ...[]byte) (key []byte) {
-	var hashMap = map[string]hash.Hash{
+	hashMap := map[string]hash.Hash{
 		"md4":        md4.New(),
 		"md5":        md5.New(),
 		"ripemd-160": ripemd160.New(),
@@ -535,8 +539,7 @@ func crypt(encrypt bool, cipherAlgorithm, cipherChaining string, key, iv, input
 // cryptPackage encrypt / decrypt package by given packageKey and encryption
 // info.
 func cryptPackage(encrypt bool, packageKey, input []byte, encryption Encryption) (outputChunks []byte, err error) {
-	encryptedKey := encryption.KeyData
-	var offset = packageOffset
+	encryptedKey, offset := encryption.KeyData, packageOffset
 	if encrypt {
 		offset = 0
 	}
diff --git a/datavalidation.go b/datavalidation.go
index c8c9141..b8f939b 100644
--- a/datavalidation.go
+++ b/datavalidation.go
@@ -199,7 +199,6 @@ func convDataValidationType(t DataValidationType) string {
 	}
 
 	return typeMap[t]
-
 }
 
 // convDataValidationOperator get excel data validation operator.
@@ -216,7 +215,6 @@ func convDataValidationOperator(o DataValidationOperator) string {
 	}
 
 	return typeMap[o]
-
 }
 
 // AddDataValidation provides set data validation on a range of the worksheet
diff --git a/date.go b/date.go
index 9923f9f..04c9110 100644
--- a/date.go
+++ b/date.go
@@ -82,7 +82,6 @@ func shiftJulianToNoon(julianDays, julianFraction float64) (float64, float64) {
 // minutes, seconds and nanoseconds that comprised a given fraction of a day.
 // values would round to 1 us.
 func fractionOfADay(fraction float64) (hours, minutes, seconds, nanoseconds int) {
-
 	const (
 		c1us  = 1e3
 		c1s   = 1e9
@@ -137,7 +136,7 @@ func doTheFliegelAndVanFlandernAlgorithm(jd int) (day, month, year int) {
 // representation (stored as a floating point number) to a time.Time.
 func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
 	var date time.Time
-	var wholeDaysPart = int(excelTime)
+	wholeDaysPart := int(excelTime)
 	// Excel uses Julian dates prior to March 1st 1900, and Gregorian
 	// thereafter.
 	if wholeDaysPart <= 61 {
@@ -152,7 +151,7 @@ func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
 		}
 		return date
 	}
-	var floatPart = excelTime - float64(wholeDaysPart) + roundEpsilon
+	floatPart := excelTime - float64(wholeDaysPart) + roundEpsilon
 	if date1904 {
 		date = excel1904Epoc
 	} else {
diff --git a/docProps.go b/docProps.go
index 770ed1a..44c30c8 100644
--- a/docProps.go
+++ b/docProps.go
@@ -101,7 +101,7 @@ func (f *File) SetAppProps(appProperties *AppProperties) (err error) {
 
 // GetAppProps provides a function to get document application properties.
 func (f *File) GetAppProps() (ret *AppProperties, err error) {
-	var app = new(xlsxProperties)
+	app := new(xlsxProperties)
 	if err = f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(f.readXML(defaultXMLPathDocPropsApp)))).
 		Decode(app); err != nil && err != io.EOF {
 		err = fmt.Errorf("xml decode error: %s", err)
@@ -204,8 +204,7 @@ func (f *File) SetDocProps(docProperties *DocProperties) (err error) {
 		Category:       core.Category,
 		Version:        core.Version,
 	}, nil
-	newProps.Created.Text, newProps.Created.Type, newProps.Modified.Text, newProps.Modified.Type =
-		core.Created.Text, core.Created.Type, core.Modified.Text, core.Modified.Type
+	newProps.Created.Text, newProps.Created.Type, newProps.Modified.Text, newProps.Modified.Type = core.Created.Text, core.Created.Type, core.Modified.Text, core.Modified.Type
 	fields = []string{
 		"Category", "ContentStatus", "Creator", "Description", "Identifier", "Keywords",
 		"LastModifiedBy", "Revision", "Subject", "Title", "Language", "Version",
@@ -230,7 +229,7 @@ func (f *File) SetDocProps(docProperties *DocProperties) (err error) {
 
 // GetDocProps provides a function to get document core properties.
 func (f *File) GetDocProps() (ret *DocProperties, err error) {
-	var core = new(decodeCoreProperties)
+	core := new(decodeCoreProperties)
 
 	if err = f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(f.readXML(defaultXMLPathDocPropsCore)))).
 		Decode(core); err != nil && err != io.EOF {
diff --git a/drawing.go b/drawing.go
index be4583c..ac88032 100644
--- a/drawing.go
+++ b/drawing.go
@@ -157,7 +157,8 @@ func (f *File) addChart(formatSet *formatChart, comboCharts []*formatChart) {
 				Cmpd: "sng",
 				Algn: "ctr",
 				SolidFill: &aSolidFill{
-					SchemeClr: &aSchemeClr{Val: "tx1",
+					SchemeClr: &aSchemeClr{
+						Val: "tx1",
 						LumMod: &attrValInt{
 							Val: intPtr(15000),
 						},
@@ -941,7 +942,8 @@ func (f *File) drawChartDLbls(formatSet *formatChart) *cDLbls {
 func (f *File) drawChartSeriesDLbls(formatSet *formatChart) *cDLbls {
 	dLbls := f.drawChartDLbls(formatSet)
 	chartSeriesDLbls := map[string]*cDLbls{
-		Scatter: nil, Surface3D: nil, WireframeSurface3D: nil, Contour: nil, WireframeContour: nil, Bubble: nil, Bubble3D: nil}
+		Scatter: nil, Surface3D: nil, WireframeSurface3D: nil, Contour: nil, WireframeContour: nil, Bubble: nil, Bubble3D: nil,
+	}
 	if _, ok := chartSeriesDLbls[formatSet.Type]; ok {
 		return nil
 	}
@@ -1194,8 +1196,7 @@ func (f *File) addDrawingChart(sheet, drawingXML, cell string, width, height, rI
 
 	width = int(float64(width) * formatSet.XScale)
 	height = int(float64(height) * formatSet.YScale)
-	colStart, rowStart, colEnd, rowEnd, x2, y2 :=
-		f.positionObjectPixels(sheet, colIdx, rowIdx, formatSet.OffsetX, formatSet.OffsetY, width, height)
+	colStart, rowStart, colEnd, rowEnd, x2, y2 := f.positionObjectPixels(sheet, colIdx, rowIdx, formatSet.OffsetX, formatSet.OffsetY, width, height)
 	content, cNvPrID := f.drawingParser(drawingXML)
 	twoCellAnchor := xdrCellAnchor{}
 	twoCellAnchor.EditAs = formatSet.Positioning
diff --git a/errors.go b/errors.go
index 8368fee..ebbcef6 100644
--- a/errors.go
+++ b/errors.go
@@ -106,6 +106,9 @@ var (
 	// ErrImgExt defined the error message on receive an unsupported image
 	// extension.
 	ErrImgExt = errors.New("unsupported image extension")
+	// ErrWorkbookExt defined the error message on receive an unsupported
+	// workbook extension.
+	ErrWorkbookExt = errors.New("unsupported workbook extension")
 	// ErrMaxFileNameLength defined the error message on receive the file name
 	// length overflow.
 	ErrMaxFileNameLength = errors.New("file name length exceeds maximum limit")
diff --git a/excelize.go b/excelize.go
index 6100ac4..2155f0a 100644
--- a/excelize.go
+++ b/excelize.go
@@ -327,7 +327,7 @@ func checkSheetR0(ws *xlsxWorksheet, sheetData *xlsxSheetData, r0 *xlsxRow) {
 // addRels provides a function to add relationships by given XML path,
 // relationship type, target and target mode.
 func (f *File) addRels(relPath, relType, target, targetMode string) int {
-	var uniqPart = map[string]string{
+	uniqPart := map[string]string{
 		SourceRelationshipSharedStrings: "/xl/sharedStrings.xml",
 	}
 	rels := f.relsReader(relPath)
@@ -434,7 +434,6 @@ func (f *File) AddVBAProject(bin string) error {
 	if path.Ext(bin) != ".bin" {
 		return ErrAddVBAProject
 	}
-	f.setContentTypePartVBAProjectExtensions()
 	wb := f.relsReader(f.getWorkbookRelsPath())
 	wb.Lock()
 	defer wb.Unlock()
@@ -463,9 +462,9 @@ func (f *File) AddVBAProject(bin string) error {
 	return err
 }
 
-// setContentTypePartVBAProjectExtensions provides a function to set the
-// content type for relationship parts and the main document part.
-func (f *File) setContentTypePartVBAProjectExtensions() {
+// setContentTypePartProjectExtensions provides a function to set the content
+// type for relationship parts and the main document part.
+func (f *File) setContentTypePartProjectExtensions(contentType string) {
 	var ok bool
 	content := f.contentTypesReader()
 	content.Lock()
@@ -477,7 +476,7 @@ func (f *File) setContentTypePartVBAProjectExtensions() {
 	}
 	for idx, o := range content.Overrides {
 		if o.PartName == "/xl/workbook.xml" {
-			content.Overrides[idx].ContentType = ContentTypeMacro
+			content.Overrides[idx].ContentType = contentType
 		}
 	}
 	if !ok {
diff --git a/excelize_test.go b/excelize_test.go
index c78797d..1548cc6 100644
--- a/excelize_test.go
+++ b/excelize_test.go
@@ -175,7 +175,10 @@ func TestSaveFile(t *testing.T) {
 	if !assert.NoError(t, err) {
 		t.FailNow()
 	}
-	assert.NoError(t, f.SaveAs(filepath.Join("test", "TestSaveFile.xlsx")))
+	assert.EqualError(t, f.SaveAs(filepath.Join("test", "TestSaveFile.xlsb")), ErrWorkbookExt.Error())
+	for _, ext := range []string{".xlam", ".xlsm", ".xlsx", ".xltm", ".xltx"} {
+		assert.NoError(t, f.SaveAs(filepath.Join("test", fmt.Sprintf("TestSaveFile%s", ext))))
+	}
 	assert.NoError(t, f.Close())
 	f, err = OpenFile(filepath.Join("test", "TestSaveFile.xlsx"))
 	if !assert.NoError(t, err) {
@@ -189,7 +192,7 @@ func TestSaveAsWrongPath(t *testing.T) {
 	f, err := OpenFile(filepath.Join("test", "Book1.xlsx"))
 	assert.NoError(t, err)
 	// Test write file to not exist directory.
-	assert.EqualError(t, f.SaveAs(""), "open .: is a directory")
+	assert.Error(t, f.SaveAs(filepath.Join("x", "Book1.xlsx")))
 	assert.NoError(t, f.Close())
 }
 
@@ -1305,7 +1308,8 @@ func TestDeleteSheetFromWorkbookRels(t *testing.T) {
 
 func TestAttrValToInt(t *testing.T) {
 	_, err := attrValToInt("r", []xml.Attr{
-		{Name: xml.Name{Local: "r"}, Value: "s"}})
+		{Name: xml.Name{Local: "r"}, Value: "s"},
+	})
 	assert.EqualError(t, err, `strconv.Atoi: parsing "s": invalid syntax`)
 }
 
diff --git a/file.go b/file.go
index 1f2b772..43d94b2 100644
--- a/file.go
+++ b/file.go
@@ -70,6 +70,17 @@ func (f *File) SaveAs(name string, opt ...Options) error {
 		return ErrMaxFileNameLength
 	}
 	f.Path = name
+	contentType, ok := map[string]string{
+		".xlam": ContentTypeAddinMacro,
+		".xlsm": ContentTypeMacro,
+		".xlsx": ContentTypeSheetML,
+		".xltm": ContentTypeTemplateMacro,
+		".xltx": ContentTypeTemplate,
+	}[filepath.Ext(f.Path)]
+	if !ok {
+		return ErrWorkbookExt
+	}
+	f.setContentTypePartProjectExtensions(contentType)
 	file, err := os.OpenFile(filepath.Clean(name), os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0600)
 	if err != nil {
 		return err
diff --git a/lib.go b/lib.go
index caaeab2..a435452 100644
--- a/lib.go
+++ b/lib.go
@@ -490,7 +490,7 @@ func parseFormatSet(formatSet string) []byte {
 // namespaceStrictToTransitional provides a method to convert Strict and
 // Transitional namespaces.
 func namespaceStrictToTransitional(content []byte) []byte {
-	var namespaceTranslationDic = map[string]string{
+	namespaceTranslationDic := map[string]string{
 		StrictSourceRelationship:               SourceRelationship.Value,
 		StrictSourceRelationshipOfficeDocument: SourceRelationshipOfficeDocument,
 		StrictSourceRelationshipChart:          SourceRelationshipChart,
@@ -611,8 +611,8 @@ func getXMLNamespace(space string, attr []xml.Attr) string {
 // replaceNameSpaceBytes provides a function to replace the XML root element
 // attribute by the given component part path and XML content.
 func (f *File) replaceNameSpaceBytes(path string, contentMarshal []byte) []byte {
-	var oldXmlns = []byte(`xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">`)
-	var newXmlns = []byte(templateNamespaceIDMap)
+	oldXmlns := []byte(`xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">`)
+	newXmlns := []byte(templateNamespaceIDMap)
 	if attr, ok := f.xmlAttr[path]; ok {
 		newXmlns = []byte(genXMLNamespace(attr))
 	}
diff --git a/lib_test.go b/lib_test.go
index 3346acc..da75dee 100644
--- a/lib_test.go
+++ b/lib_test.go
@@ -159,7 +159,6 @@ func TestJoinCellName_Error(t *testing.T) {
 			test(col.Name, row)
 		}
 	}
-
 }
 
 func TestCellNameToCoordinates_OK(t *testing.T) {
diff --git a/picture.go b/picture.go
index 9429f4a..f018bd9 100644
--- a/picture.go
+++ b/picture.go
@@ -209,7 +209,7 @@ func (f *File) deleteSheetRelationships(sheet, rID string) {
 	if !ok {
 		name = strings.ToLower(sheet) + ".xml"
 	}
-	var rels = "xl/worksheets/_rels/" + strings.TrimPrefix(name, "xl/worksheets/") + ".rels"
+	rels := "xl/worksheets/_rels/" + strings.TrimPrefix(name, "xl/worksheets/") + ".rels"
 	sheetRels := f.relsReader(rels)
 	if sheetRels == nil {
 		sheetRels = &xlsxRelationships{}
@@ -288,8 +288,7 @@ func (f *File) addDrawingPicture(sheet, drawingXML, cell, file string, width, he
 	}
 	col--
 	row--
-	colStart, rowStart, colEnd, rowEnd, x2, y2 :=
-		f.positionObjectPixels(sheet, col, row, formatSet.OffsetX, formatSet.OffsetY, width, height)
+	colStart, rowStart, colEnd, rowEnd, x2, y2 := f.positionObjectPixels(sheet, col, row, formatSet.OffsetX, formatSet.OffsetY, width, height)
 	content, cNvPrID := f.drawingParser(drawingXML)
 	twoCellAnchor := xdrCellAnchor{}
 	twoCellAnchor.EditAs = formatSet.Positioning
@@ -372,7 +371,7 @@ func (f *File) addMedia(file []byte, ext string) string {
 // setContentTypePartImageExtensions provides a function to set the content
 // type for relationship parts and the Main Document part.
 func (f *File) setContentTypePartImageExtensions() {
-	var imageTypes = map[string]bool{"jpeg": false, "png": false, "gif": false, "tiff": false}
+	imageTypes := map[string]bool{"jpeg": false, "png": false, "gif": false, "tiff": false}
 	content := f.contentTypesReader()
 	content.Lock()
 	defer content.Unlock()
@@ -465,7 +464,7 @@ func (f *File) getSheetRelationshipsTargetByID(sheet, rID string) string {
 	if !ok {
 		name = strings.ToLower(sheet) + ".xml"
 	}
-	var rels = "xl/worksheets/_rels/" + strings.TrimPrefix(name, "xl/worksheets/") + ".rels"
+	rels := "xl/worksheets/_rels/" + strings.TrimPrefix(name, "xl/worksheets/") + ".rels"
 	sheetRels := f.relsReader(rels)
 	if sheetRels == nil {
 		sheetRels = &xlsxRelationships{}
diff --git a/picture_test.go b/picture_test.go
index 5bf139d..8da7c3d 100644
--- a/picture_test.go
+++ b/picture_test.go
@@ -1,19 +1,18 @@
 package excelize
 
 import (
+	"fmt"
 	_ "image/gif"
 	_ "image/jpeg"
 	_ "image/png"
-
-	_ "golang.org/x/image/tiff"
-
-	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
 	"testing"
 
+	_ "golang.org/x/image/tiff"
+
 	"github.com/stretchr/testify/assert"
 )
 
diff --git a/rows.go b/rows.go
index 8702f93..88df52c 100644
--- a/rows.go
+++ b/rows.go
@@ -362,7 +362,7 @@ func (f *File) GetRowHeight(sheet string, row int) (float64, error) {
 	if row < 1 {
 		return defaultRowHeightPixels, newInvalidRowNumberError(row)
 	}
-	var ht = defaultRowHeight
+	ht := defaultRowHeight
 	ws, err := f.workSheetReader(sheet)
 	if err != nil {
 		return ht, err
diff --git a/rows_test.go b/rows_test.go
index 0d2ca23..4d81e66 100644
--- a/rows_test.go
+++ b/rows_test.go
@@ -847,7 +847,8 @@ func TestDuplicateRowTo(t *testing.T) {
 	assert.Equal(t, nil, f.DuplicateRowTo(sheetName, 1, 2))
 	// Test duplicate row on the worksheet with illegal cell coordinates
 	f.Sheet.Store("xl/worksheets/sheet1.xml", &xlsxWorksheet{
-		MergeCells: &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A:B1"}}}})
+		MergeCells: &xlsxMergeCells{Cells: []*xlsxMergeCell{{Ref: "A:B1"}}},
+	})
 	assert.EqualError(t, f.DuplicateRowTo(sheetName, 1, 2), newCellNameToCoordinatesError("A", newInvalidCellNameError("A")).Error())
 	// Test duplicate row on not exists worksheet
 	assert.EqualError(t, f.DuplicateRowTo("SheetN", 1, 2), "sheet SheetN is not exist")
diff --git a/shape.go b/shape.go
index 974aa5f..be3735b 100644
--- a/shape.go
+++ b/shape.go
@@ -351,9 +351,8 @@ func (f *File) addDrawingShape(sheet, drawingXML, cell string, formatSet *format
 	width := int(float64(formatSet.Width) * formatSet.Format.XScale)
 	height := int(float64(formatSet.Height) * formatSet.Format.YScale)
 
-	colStart, rowStart, colEnd, rowEnd, x2, y2 :=
-		f.positionObjectPixels(sheet, colIdx, rowIdx, formatSet.Format.OffsetX, formatSet.Format.OffsetY,
-			width, height)
+	colStart, rowStart, colEnd, rowEnd, x2, y2 := f.positionObjectPixels(sheet, colIdx, rowIdx, formatSet.Format.OffsetX, formatSet.Format.OffsetY,
+		width, height)
 	content, cNvPrID := f.drawingParser(drawingXML)
 	twoCellAnchor := xdrCellAnchor{}
 	twoCellAnchor.EditAs = formatSet.Format.Positioning
diff --git a/sheet.go b/sheet.go
index 2426bf8..f10ca07 100644
--- a/sheet.go
+++ b/sheet.go
@@ -368,7 +368,7 @@ func (f *File) SetActiveSheet(index int) {
 // GetActiveSheetIndex provides a function to get active sheet index of the
 // spreadsheet. If not found the active sheet will be return integer 0.
 func (f *File) GetActiveSheetIndex() (index int) {
-	var sheetID = f.getActiveSheetID()
+	sheetID := f.getActiveSheetID()
 	wb := f.workbookReader()
 	if wb != nil {
 		for idx, sheet := range wb.Sheets.Sheet {
@@ -1723,7 +1723,7 @@ func (f *File) UngroupSheets() error {
 func (f *File) InsertPageBreak(sheet, cell string) (err error) {
 	var ws *xlsxWorksheet
 	var row, col int
-	var rowBrk, colBrk = -1, -1
+	rowBrk, colBrk := -1, -1
 	if ws, err = f.workSheetReader(sheet); err != nil {
 		return
 	}
diff --git a/sheet_test.go b/sheet_test.go
index a5c99a6..7df9018 100644
--- a/sheet_test.go
+++ b/sheet_test.go
@@ -123,7 +123,6 @@ func TestPageLayoutOption(t *testing.T) {
 
 	for i, test := range testData {
 		t.Run(fmt.Sprintf("TestData%d", i), func(t *testing.T) {
-
 			opt := test.nonDefault
 			t.Logf("option %T", opt)
 
@@ -452,6 +451,7 @@ func BenchmarkNewSheet(b *testing.B) {
 		}
 	})
 }
+
 func newSheetWithSet() {
 	file := NewFile()
 	file.NewSheet("sheet1")
diff --git a/sheetpr_test.go b/sheetpr_test.go
index 7c669e8..91685d8 100644
--- a/sheetpr_test.go
+++ b/sheetpr_test.go
@@ -108,7 +108,6 @@ func TestSheetPrOptions(t *testing.T) {
 
 	for i, test := range testData {
 		t.Run(fmt.Sprintf("TestData%d", i), func(t *testing.T) {
-
 			opt := test.nonDefault
 			t.Logf("option %T", opt)
 
@@ -258,7 +257,6 @@ func TestPageMarginsOption(t *testing.T) {
 
 	for i, test := range testData {
 		t.Run(fmt.Sprintf("TestData%d", i), func(t *testing.T) {
-
 			opt := test.nonDefault
 			t.Logf("option %T", opt)
 
@@ -395,7 +393,6 @@ func TestSheetFormatPrOptions(t *testing.T) {
 
 	for i, test := range testData {
 		t.Run(fmt.Sprintf("TestData%d", i), func(t *testing.T) {
-
 			opt := test.nonDefault
 			t.Logf("option %T", opt)
 
diff --git a/sheetview_test.go b/sheetview_test.go
index e323e23..9207dec 100644
--- a/sheetview_test.go
+++ b/sheetview_test.go
@@ -81,7 +81,6 @@ func ExampleFile_SetSheetViewOptions() {
 	// - zoomScale: 80
 	// Used correct value:
 	// - zoomScale: 123
-
 }
 
 func ExampleFile_GetSheetViewOptions() {
diff --git a/styles.go b/styles.go
index 261e3df..5c887db 100644
--- a/styles.go
+++ b/styles.go
@@ -963,7 +963,7 @@ func parseTime(v string, format string) string {
 	goFmt = format
 
 	if strings.Contains(goFmt, "[") {
-		var re = regexp.MustCompile(`\[.+\]`)
+		re := regexp.MustCompile(`\[.+\]`)
 		goFmt = re.ReplaceAllLiteralString(goFmt, "")
 	}
 
@@ -2388,7 +2388,7 @@ func getFillID(styleSheet *xlsxStyleSheet, style *Style) (fillID int) {
 // newFills provides a function to add fill elements in the styles.xml by
 // given cell format settings.
 func newFills(style *Style, fg bool) *xlsxFill {
-	var patterns = []string{
+	patterns := []string{
 		"none",
 		"solid",
 		"mediumGray",
@@ -2410,7 +2410,7 @@ func newFills(style *Style, fg bool) *xlsxFill {
 		"gray0625",
 	}
 
-	var variants = []float64{
+	variants := []float64{
 		90,
 		0,
 		45,
@@ -2522,7 +2522,7 @@ func getBorderID(styleSheet *xlsxStyleSheet, style *Style) (borderID int) {
 // newBorders provides a function to add border elements in the styles.xml by
 // given borders format settings.
 func newBorders(style *Style) *xlsxBorder {
-	var styles = []string{
+	styles := []string{
 		"none",
 		"thin",
 		"medium",
diff --git a/templates.go b/templates.go
index 81b2c20..d08f45f 100644
--- a/templates.go
+++ b/templates.go
@@ -16,11 +16,9 @@ package excelize
 
 import "encoding/xml"
 
-var (
-	// XMLHeaderByte define an XML declaration can also contain a standalone
-	// declaration.
-	XMLHeaderByte = []byte(xml.Header)
-)
+// XMLHeaderByte define an XML declaration can also contain a standalone
+// declaration.
+var XMLHeaderByte = []byte(xml.Header)
 
 const (
 	defaultXMLPathContentTypes  = "[Content_Types].xml"
diff --git a/xmlDrawing.go b/xmlDrawing.go
index f51451b..61c25ca 100644
--- a/xmlDrawing.go
+++ b/xmlDrawing.go
@@ -65,7 +65,11 @@ const (
 	NameSpaceDublinCoreMetadataInitiative        = "http://purl.org/dc/dcmitype/"
 	ContentTypeDrawing                           = "application/vnd.openxmlformats-officedocument.drawing+xml"
 	ContentTypeDrawingML                         = "application/vnd.openxmlformats-officedocument.drawingml.chart+xml"
+	ContentTypeSheetML                           = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"
+	ContentTypeTemplate                          = "application/vnd.openxmlformats-officedocument.spreadsheetml.template.main+xml"
+	ContentTypeAddinMacro                        = "application/vnd.ms-excel.addin.macroEnabled.main+xml"
 	ContentTypeMacro                             = "application/vnd.ms-excel.sheet.macroEnabled.main+xml"
+	ContentTypeTemplateMacro                     = "application/vnd.ms-excel.template.macroEnabled.main+xml"
 	ContentTypeSpreadSheetMLChartsheet           = "application/vnd.openxmlformats-officedocument.spreadsheetml.chartsheet+xml"
 	ContentTypeSpreadSheetMLComments             = "application/vnd.openxmlformats-officedocument.spreadsheetml.comments+xml"
 	ContentTypeSpreadSheetMLPivotCacheDefinition = "application/vnd.openxmlformats-officedocument.spreadsheetml.pivotCacheDefinition+xml"
diff --git a/xmlPivotCache.go b/xmlPivotCache.go
index 7f3dac0..9591858 100644
--- a/xmlPivotCache.go
+++ b/xmlPivotCache.go
@@ -79,8 +79,7 @@ type xlsxWorksheetSource struct {
 // PivotTable is a collection of ranges in the workbook. The ranges are
 // specified in the rangeSets collection. The logic for how the application
 // consolidates the data in the ranges is application- defined.
-type xlsxConsolidation struct {
-}
+type xlsxConsolidation struct{}
 
 // xlsxCacheFields represents the collection of field definitions in the
 // source data.
@@ -144,8 +143,7 @@ type xlsxSharedItems struct {
 }
 
 // xlsxMissing represents a value that was not specified.
-type xlsxMissing struct {
-}
+type xlsxMissing struct{}
 
 // xlsxNumber represents a numeric value in the PivotTable.
 type xlsxNumber struct {
@@ -167,18 +165,15 @@ type xlsxNumber struct {
 
 // xlsxTuples represents members for the OLAP sheet data entry, also known as
 // a tuple.
-type xlsxTuples struct {
-}
+type xlsxTuples struct{}
 
 // xlsxBoolean represents a boolean value for an item in the PivotTable.
-type xlsxBoolean struct {
-}
+type xlsxBoolean struct{}
 
 // xlsxError represents an error value. The use of this item indicates that an
 // error value is present in the PivotTable source. The error is recorded in
 // the value attribute.
-type xlsxError struct {
-}
+type xlsxError struct{}
 
 // xlsxString represents a character value in a PivotTable.
 type xlsxString struct {
@@ -199,45 +194,35 @@ type xlsxString struct {
 }
 
 // xlsxDateTime represents a date-time value in the PivotTable.
-type xlsxDateTime struct {
-}
+type xlsxDateTime struct{}
 
 // xlsxFieldGroup represents the collection of properties for a field group.
-type xlsxFieldGroup struct {
-}
+type xlsxFieldGroup struct{}
 
 // xlsxCacheHierarchies represents the collection of OLAP hierarchies in the
 // PivotCache.
-type xlsxCacheHierarchies struct {
-}
+type xlsxCacheHierarchies struct{}
 
 // xlsxKpis represents the collection of Key Performance Indicators (KPIs)
 // defined on the OLAP server and stored in the PivotCache.
-type xlsxKpis struct {
-}
+type xlsxKpis struct{}
 
 // xlsxTupleCache represents the cache of OLAP sheet data members, or tuples.
-type xlsxTupleCache struct {
-}
+type xlsxTupleCache struct{}
 
 // xlsxCalculatedItems represents the collection of calculated items.
-type xlsxCalculatedItems struct {
-}
+type xlsxCalculatedItems struct{}
 
 // xlsxCalculatedMembers represents the collection of calculated members in an
 // OLAP PivotTable.
-type xlsxCalculatedMembers struct {
-}
+type xlsxCalculatedMembers struct{}
 
 // xlsxDimensions represents the collection of PivotTable OLAP dimensions.
-type xlsxDimensions struct {
-}
+type xlsxDimensions struct{}
 
 // xlsxMeasureGroups represents the collection of PivotTable OLAP measure
 // groups.
-type xlsxMeasureGroups struct {
-}
+type xlsxMeasureGroups struct{}
 
 // xlsxMaps represents the PivotTable OLAP measure group - Dimension maps.
-type xlsxMaps struct {
-}
+type xlsxMaps struct{}
diff --git a/xmlPivotTable.go b/xmlPivotTable.go
index 38dfb1e..a7543a7 100644
--- a/xmlPivotTable.go
+++ b/xmlPivotTable.go
@@ -195,8 +195,7 @@ type xlsxItem struct {
 }
 
 // xlsxAutoSortScope represents the sorting scope for the PivotTable.
-type xlsxAutoSortScope struct {
-}
+type xlsxAutoSortScope struct{}
 
 // xlsxRowFields represents the collection of row fields for the PivotTable.
 type xlsxRowFields struct {
@@ -225,8 +224,7 @@ type xlsxI struct {
 }
 
 // xlsxX represents an array of indexes to cached shared item values.
-type xlsxX struct {
-}
+type xlsxX struct{}
 
 // xlsxColFields represents the collection of fields that are on the column
 // axis of the PivotTable.
@@ -281,8 +279,7 @@ type xlsxDataField struct {
 
 // xlsxConditionalFormats represents the collection of conditional formats
 // applied to a PivotTable.
-type xlsxConditionalFormats struct {
-}
+type xlsxConditionalFormats struct{}
 
 // xlsxPivotTableStyleInfo represent information on style applied to the
 // PivotTable.