code: func (v *EmailIsPresent) IsValid(errors *validate.Errors) {
  	if !rxEmail.Match([]byte(v.Field)) {
  		if v.Message == "" {
  			v.Message = fmt.Sprintf("%s does not match the email format.", v.Name)
  		}
  		errors.Add(GenerateKey(v.Name), v.Message)
  	}
  }
docs: // IsValid performs the validation based on the email regexp match.