code: func (c *Client) SendMail(data *InfoSendMail) (res *SentResult, err error) {
  	url := c.apiBase + "/send/message"
  	req, err := createRequest("POST", url, data, nil)
  	if err != nil {
  		return res, err
  	}
  
  	headers := map[string]string{"Content-Type": "application/json"}
  
  	c.Lock()
  	defer c.Unlock()
  	_, _, err = c.httpClient.Send(req).With(headers).Read(&res).Call()
  	return res, err
  }
docs: // SendMail send mail via API.