code: func (c *Client) Send(msg OMessage) error {
  	buf, err := json.Marshal(msg)
  	if err != nil {
  		return err
  	}
  	resp, err := c.httpclient.Post(c.Url, "application/json", bytes.NewReader(buf))
  	if err != nil {
  		return err
  	}
  	defer resp.Body.Close()
  
  	// Read entire body to completion to re-use keep-alive connections.
  	io.Copy(ioutil.Discard, resp.Body)
  
  	if resp.StatusCode != 200 {
  		return fmt.Errorf("unexpected status code: %d", resp.StatusCode)
  	}
  	return nil
  }
docs: // Send sends a msg to mattermost incoming webhooks URL.