code: func StringLength(str string, params ...string) bool {
  
  	if len(params) == 2 {
  		strLength := utf8.RuneCountInString(str)
  		min, _ := ToInt(params[0])
  		max, _ := ToInt(params[1])
  		return strLength >= int(min) && strLength <= int(max)
  	}
  
  	return false
  }
docs: // StringLength check string's length (including multi byte strings)