code: func (i *Image) getResponseFromURL(u string) (*http.Response, error) {
  	req, err := http.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, err
  	}
  	req.Header.Set("Authorization", "Token "+i.token)
  
  	res, err := i.client.Do(req)
  	if err != nil {
  		return nil, err
  	}
  
  	if res.StatusCode != http.StatusOK {
  		defer res.Body.Close()
  		type errorMsg struct {
  			Error string `json:"error"`
  		}
  
  		var errMsg errorMsg
  		if err := json.NewDecoder(res.Body).Decode(&errMsg); err == nil {
  			return nil, fmt.Errorf("%s: HTTP %d - %s", u, res.StatusCode, errMsg.Error)
  		}
  
  		return nil, fmt.Errorf("%s: HTTP %d", u, res.StatusCode)
  	}
  
  	return res, nil
  }
docs: // getAPIResponseFromURL returns raw Docker API response at URL 'u'.