code: func getWorksheetFromSheet(sheet xlsxSheet, worksheets map[string]*zip.File, sheetXMLMap map[string]string, rowLimit int) (*xlsxWorksheet, error) {
  	var r io.Reader
  	var decoder *xml.Decoder
  	var worksheet *xlsxWorksheet
  	var err error
  	worksheet = new(xlsxWorksheet)
  
  	f := worksheetFileForSheet(sheet, worksheets, sheetXMLMap)
  	if f == nil {
  		return nil, fmt.Errorf("Unable to find sheet '%s'", sheet)
  	}
  	if rc, err := f.Open(); err != nil {
  		return nil, err
  	} else {
  		defer rc.Close()
  		r = rc
  	}
  
  	if rowLimit != NoRowLimit {
  		r, err = truncateSheetXML(r, rowLimit)
  		if err != nil {
  			return nil, err
  		}
  	}
  
  	decoder = xml.NewDecoder(r)
  	err = decoder.Decode(worksheet)
  	if err != nil {
  		return nil, err
  	}
  	return worksheet, nil
  }
docs: // getWorksheetFromSheet() is an internal helper function to open a
  // sheetN.xml file, referred to by an xlsx.xlsxSheet struct, from the XLSX
  // file and unmarshal it an xlsx.xlsxWorksheet struct