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, 3 insertions, 3 deletions

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))
 	}