code: func HTTPBody(handler http.HandlerFunc, method, url string, values url.Values) string {
  	w := httptest.NewRecorder()
  	req, err := http.NewRequest(method, url+"?"+values.Encode(), nil)
  	if err != nil {
  		return ""
  	}
  	handler(w, req)
  	return w.Body.String()
  }
docs: // HTTPBody is a helper that returns HTTP body of the response. It returns
  // empty string if building a new request fails.