code: func pubSubPush(c *router.Context) {
  	processPubSubRequest(c.Context, c.Writer, c.Request, func(ctx context.Context, srv authService, serviceURL string) (*service.Notification, error) {
  		body, err := ioutil.ReadAll(c.Request.Body)
  		if err != nil {
  			return nil, err
  		}
  		return srv.ProcessPubSubPush(ctx, body)
  	})
  }
docs: // pubSubPush is HTTP handler that processes incoming PubSub push notifications.
  //
  // It uses the signature inside PubSub message body for authentication. Skips
  // messages not signed by currently configured auth service.