Make case-insensitive for the workbook extension name

[playGitboy]

比如

f := excelize.NewFile()
f.SaveAs("D:\\Temp\\test.XLsx")
f.Close()

会发现test.XLsx文件并未生成

调试查看file.go文件SaveAs函数，发现关键点应在

contentType, ok := map[string]string{
  ".xlam": ContentTypeAddinMacro,
  ".xlsm": ContentTypeMacro,
  ".xlsx": ContentTypeSheetML,
  ".xltm": ContentTypeTemplateMacro,
  ".xltx": ContentTypeTemplate,
}[filepath.Ext(f.Path)]

后面修改为strings.ToLower(filepath.Ext(f.Path))可解决增强容错

Version: Excelize [email protected]

[xuri]

Thanks for your issue. Would you like to create a pull request to fix that?

[playGitboy]

Thanks for your issue. Would you like to create a pull request to fix that?

Sorry, the first pull request is not very familiar, I don't know if the submission is compliant.

[xuri]

Thanks for your contribution. This patch will be released in the next version.