code: func (cm *connectMethod) proxyAuth() string {
  	if cm.proxyURL == nil {
  		return ""
  	}
  	if u := cm.proxyURL.User; u != nil {
  		return "Basic " + base64.URLEncoding.EncodeToString([]byte(u.String()))
  	}
  	return ""
  }
docs: // proxyAuth returns the Proxy-Authorization header to set
  // on requests, if applicable.