GoVPP CLI: worker to main thread when using api : communication problem ? about govpp HOT 2 OPEN

func doPing(conn api.Connection) {
	sub, err := conn.WatchEvent(context.Background(), (*ping.PingFinishedEvent)(nil))
	if err != nil {
		log.Fatalln("ERROR:", err)
	}
	var wg sync.WaitGroup
	wg.Add(1)


	go func() {
		fmt.Println("waiting for events")
		defer fmt.Println("done waiting for events")

		for notif := range sub.Events() {
			e, ok := notif.(*ping.PingFinishedEvent)
			if !ok {
				fmt.Printf("invalid notification type: %#v\n", e)
				continue
			}
			fmt.Printf("Ping %+v\n", e)
			wg.Done()
		}
	}()

	c := ping.NewServiceClient(conn)

	reply, err := c.WantPingFinishedEvents(context.Background(), &ping.WantPingFinishedEvents{
		Address: ip_types.NewAddress(net.ParseIP("20.0.0.2")),
		Repeat: 10,
		Interval: 1.0,
	})
	if err != nil {
		log.Fatalln("ERROR:", err)
	}
	fmt.Printf("ping ok: %+v\n", reply)
	wg.Wait()
}