code: func (rec *Recording) DownloadFile(client *messagebird.Client) (io.ReadCloser, error) {
  	req, err := http.NewRequest(http.MethodGet, apiRoot+rec.links["file"], nil)
  	if err != nil {
  		return nil, err
  	}
  	req.Header.Set("Accept", "audio/*")
  	req.Header.Set("Authorization", "AccessKey "+client.AccessKey)
  	req.Header.Set("User-Agent", "MessageBird/ApiClient/"+messagebird.ClientVersion+" Go/"+runtime.Version())
  
  	resp, err := client.HTTPClient.Do(req)
  	if err != nil {
  		return nil, err
  	}
  	if resp.StatusCode != http.StatusOK {
  		return nil, fmt.Errorf("bad HTTP status: %d", resp.StatusCode)
  	}
  	return resp.Body, nil
  }
docs: // DownloadFile streams the recorded WAV file.