When using GetSheetMap(), the result map only contain last sheet

[mrdundun]

When using GetSheetMap(), the result map only contain last sheet

When I parse xlsx file by using GetSheetMap(), the result map only contain one sheet(the last sheet).But actually there are about 70 sheets.

when I debug into the implement of GetSheetMap(), I found that err occurs here:

rID, _ := strconv.Atoi(strings.TrimSuffix(strings.TrimPrefix(rel.Target, "worksheets/sheet"), ".xml"))

The value of rel.Target is "/xl/worksheets/sheet1.xml", and convert failed.
The value of rID always be "0".The next sheet always replace the previous.
I thing that's why the result map only contain the last sheet.

Steps to reproduce the issue:

        xlsx, err := excelize.OpenFile("./1.xlsx")
	if err != nil {
		fmt.Println(err)
		return false
	}

	for index, name := range xlsx.GetSheetMap() {
		fmt.Println(index, name)
	}

Output of go version:

go version go1.9.2 darwin/amd64

Excelize version or commit ID:

1.4 

Environment details (OS, Microsoft Excel™ version, physical, etc.):
Mac OS 10.13.6
1.xlsx