code: func (c *Client) Get(mr *Request, resp interface{}, options ...RequestOptions) (err error) {
  	url := buildURL(c.apiBase, mr)
  	req, err := createRequest("GET", url, nil, nil, options...)
  	if err != nil {
  		return err
  	}
  
  	c.Lock()
  	defer c.Unlock()
  	_, _, err = c.httpClient.Send(req).Read(resp).Call()
  	return err
  }
docs: // Get issues a GET to view a resource specifying an id
  // and stores the result in the value pointed to by res.
  // Filters can be add via functional options.
  // Without an specified ID in MailjetRequest, it is the same as List.