code: func hasMultiByteCharacter(fl FieldLevel) bool {
  
  	field := fl.Field()
  
  	if field.Len() == 0 {
  		return true
  	}
  
  	return multibyteRegex.MatchString(field.String())
  }
docs: // HasMultiByteCharacter is the validation function for validating if the field's value has a multi byte character.