The frame is lost in request response about zmq4 HOT 1 CLOSED

go goresponder()
go gorequester()
time.Sleep(12 * time.Second)

log.SetPrefix("rrclient: ")

req := zmq4.NewReq(context.Background())
defer req.Close()

err := req.Dial("tcp://localhost:5559")
if err != nil {
	log.Fatalf("could not dial: %v", err)
}

for i := 0; i < 10; i++ {
	err := req.Send(zmq4.NewMsgFromString([]string {"Hello?","Hello!"}))
	if err != nil {
		log.Fatalf("could not send greeting: %v", err)
	}

	msg, err := req.Recv()
	if err != nil {
		log.Fatalf("could not recv greeting: %v", err)
	}
	log.Printf("received reply %d [%s]\n", i, msg.Frames[0])
}

//  Socket to talk to clients
rep := zmq4.NewRep(context.Background())
defer rep.Close()

err := rep.Listen("tcp://*:5559")
if err != nil {
	log.Fatalf("could not dial: %v", err)
}

for {
	//  Wait for next request from client
	msg, err := rep.Recv()
	if err != nil {
		log.Fatalf("could not recv request: %v", err)
	}

	log.Printf("received request: [%s]\n", msg.Frames[0])

	//  Do some 'work'
	time.Sleep(time.Second)

	//  Send reply back to client
	err = rep.Send(zmq4.NewMsgString("World"))
	if err != nil {
		log.Fatalf("could not send reply: %v", err)
	}
}