code: func (sb *StreamFileBuilder) AddValidation(sheetIndex, colIndex, rowStartIndex int, validation *xlsxCellDataValidation) {
  	sheet := sb.xlsxFile.Sheets[sheetIndex]
  	column := sheet.Col(colIndex)
  	column.SetDataValidationWithStart(validation, rowStartIndex)
  }
docs: // AddValidation will add a validation to a specific column.