code: func (mail *mailer) sendMail(subject, message string) error {
  	addr := strings.Split(mail.Addr, ":")
  	if len(addr) != 2 {
  		return errors.New("invalid Mail Address")
  	}
  	host := addr[0]
  	msg := []byte("To:" + strings.Join(mail.To, ";") +
  		"\r\nFrom: " + mail.From +
  		"\r\nSubject: " + subject +
  		"\r\nContent-Type: text/plain\r\n\r\n" +
  		message)
  	auth := smtp.PlainAuth(
  		"",
  		mail.Username,
  		mail.Password,
  		host,
  	)
  	err := smtp.SendMail(
  		mail.Addr,
  		auth,
  		mail.From,
  		mail.To,
  		msg,
  	)
  	if err != nil {
  		return err
  	}
  	return nil
  }
docs: // sendMail allows users to send email, only if mail parameters is configured correctly.