code: func NewSPDYExecutor(config *restclient.Config, method string, url *url.URL) (Executor, error) {
  	wrapper, upgradeRoundTripper, err := spdy.RoundTripperFor(config)
  	if err != nil {
  		return nil, err
  	}
  	return NewSPDYExecutorForTransports(wrapper, upgradeRoundTripper, method, url)
  }
docs: // NewSPDYExecutor connects to the provided server and upgrades the connection to
  // multiplexed bidirectional streams.