code: func proxyFromEnvironment(req *http.Request) (*url.URL, error) {
  	proxy := getenvEitherCase("HTTP_PROXY")
  	if proxy == "" {
  		return nil, nil
  	}
  	proxyURL, err := url.Parse(proxy)
  	if err != nil || proxyURL.Scheme == "" {
  		if u, err := url.Parse("http://" + proxy); err == nil {
  			proxyURL = u
  			err = nil
  		}
  	}
  	if err != nil {
  		return nil, fmt.Errorf("invalid proxy address %q: %v", proxy, err)
  	}
  	return proxyURL, nil
  }
docs: // proxyFromEnvironment is similar to http.ProxyFromEnvironment but it skips
  // $NO_PROXY blacklist so it proxies every requests, including localhost
  // requests.