code: func (c *ResponseClient) SendResponse(req Request, response Response) error {
  	raw, err := json.Marshal(response)
  	if err != nil {
  		return err
  	}
  
  	r, err := http.NewRequest("PUT", req.ResponseURL, bytes.NewReader(raw))
  	if err != nil {
  		return err
  	}
  
  	resp, err := c.client.Do(r)
  	if err != nil {
  		return err
  	}
  	defer resp.Body.Close()
  	body, _ := ioutil.ReadAll(resp.Body)
  
  	if code := resp.StatusCode; code/100 != 2 {
  		return fmt.Errorf("unexpected response from pre-signed url: %v: %v", code, string(body))
  	}
  
  	return nil
  }
docs: // SendResponse sends the response to the request's ResponseURL.