code: func builtinStrToDate(args []types.Datum, _ context.Context) (types.Datum, error) {
  	date := args[0].GetString()
  	format := args[1].GetString()
  	var (
  		d types.Datum
  		t types.Time
  	)
  
  	succ := t.StrToDate(date, format)
  	if !succ {
  		d.SetNull()
  		return d, nil
  	}
  
  	d.SetMysqlTime(t)
  	return d, nil
  }
docs: // See https://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_str-to-date