code: func (m *Mailer) SendMail(to []string, subject, msg string) error {
  	for _, rcpt := range to {
  		m.Messages = append(m.Messages, MailerMessage{
  			To:      rcpt,
  			Subject: subject,
  			Body:    msg,
  		})
  	}
  	return nil
  }
docs: // SendMail is a mock