code: func (w *GCWorker) Start() {
  	var ctx context.Context
  	ctx, w.cancel = context.WithCancel(context.Background())
  	var wg sync.WaitGroup
  	wg.Add(1)
  	go w.start(ctx, &wg)
  	wg.Wait() // Wait create session finish in worker, some test code depend on this to avoid race.
  }
docs: // Start starts the worker.