GetSheetName function will remove the sheet when oldSheetName is same with newSheetName

[hybnew]

Description

SetSheetName will delete the sheet if old name is equals to new name

the source code of excelize v2.3.1 is below:

func (f *File) SetSheetName(oldName, newName string) {
	oldName = trimSheetName(oldName)
	newName = trimSheetName(newName)
	content := f.workbookReader()
	for k, v := range content.Sheets.Sheet {
		if v.Name == oldName {
			content.Sheets.Sheet[k].Name = newName
			f.sheetMap[newName] = f.sheetMap[oldName]
			delete(f.sheetMap, oldName) // we may add a check if newName == oldName before
		}
	}
}

Steps to reproduce the issue:

1. get a excelize file f from Open f, err := excelize.OpenFile(g.Opts.TmplConf.TemplateLocation)
2. f.SetSheetName(oldSheetName, name)
3. f.SetCellStr(name)

Describe the results you received:
step 3 got sheet not exist
Describe the results you expected:
step 3 setCellStr err is nil.
Output of go version:

GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/yubohe 1/Library/Caches/go-build"
GOENV="/Users/yubohe 1/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/yubohe 1/go"
GOPRIVATE=""
GOPROXY="direct"
GOROOT="/usr/local/go"
GOSUMDB="off"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/y4/z855mpsx2bqb5n091wrg0zh00000gq/T/go-build327334959=/tmp/go-build -gno-record-gcc-switches -fno-common"

Excelize version or commit ID:

v2.3.1

Environment details (OS, Microsoft Excel™ version, physical, etc.):

[xuri]

Thanks for your issue, I have fixed it, please try to use the master branch code.

[hybnew]

@xuri Noted, thx , I'll upgrade when v2.3.2 release.