code: func (r *ValidationResult) MessageKey(message string, args ...interface{}) *ValidationResult {
  	if r.Error == nil {
  		return r
  	}
  
  	// If translator found, use that to create the message, otherwise call Message method
  	if r.Translator != nil {
  		r.Error.Message = r.Translator(r.Locale, message, args...)
  	} else {
  		r.Message(message, args...)
  	}
  
  	return r
  }
docs: // Allow a message key to be passed into the validation result. The Validation has already
  // setup the translator to translate the message key