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`

1 files changed, 4 insertions, 4 deletions

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",