code: func ClientTimeout(timeout time.Duration) roundtrip.ClientParam {
  	return func(c *roundtrip.Client) error {
  		transport, ok := (c.HTTPClient().Transport).(*http.Transport)
  		if !ok {
  			return nil
  		}
  		transport.IdleConnTimeout = timeout
  		transport.ResponseHeaderTimeout = timeout
  		return nil
  	}
  }
docs: // ClientTimeout sets idle and dial timeouts of the HTTP transport
  // used by the client.