Subscribe() after Listen() doesn't works

[jkralik]

When I create sub, and then Listen() and set OptionSubscribe, it never subscribe to accepted connections.

This is example of code which describe the issue:

        ctx := context.Background()
	sub := zmq4.NewSub(ctx)
	err := sub.Listen("tcp://*:1234") // listen
	if err != nil {
		log.Fatalf("could not listen: %v", err)
	}
	err = sub.SetOption(zmq4.OptionSubscribe, "") // subscribe for all messages
	if err != nil {
		log.Fatalf("could not subscribe to topic %v", err)
	}
	go func() {
		for {
			msg, err := sub.Recv() // never gets message because OptionSubscribe was not applied after connection was accepted.
			if err != nil {
				log.Printf("could not recv message: %v", err)
			} else {
				fmt.Printf("recv %+v\n", msg)
			}
		}
	}()

	pub := zmq4.NewPub(ctx)
	err = pub.Dial("tcp://*:1234")
	if err != nil {
		log.Fatalf("could not dial: %v", err)
	}
	for {
		msg := zmq4.NewMsgString("test abc")
		err := pub.Send(msg)
		if err != nil {
			log.Printf("could send message: %v", err)
		}
		fmt.Printf("msg send\n")
		time.Sleep(time.Second)
	}

Workaround: when I add one goroutine which in cycle call Subscribe() it works - but it is not effective and unreliable ...

        ctx := context.Background()
	sub := zmq4.NewSub(ctx)
	err := sub.Listen("tcp://*:1234")
	if err != nil {
		log.Fatalf("could not listen: %v", err)
	}
	err = sub.SetOption(zmq4.OptionSubscribe, "")
	if err != nil {
		log.Fatalf("could not subscribe to topic %v", err)
	}
	go func() {
		for {
			msg, err := sub.Recv()
			if err != nil {
				log.Printf("could not recv message: %v", err)
			} else {
				fmt.Printf("recv %+v\n", msg)
			}
		}
	}()

        // set subscription too all accepted socket
	go func() {
		for {
			err = sub.SetOption(zmq4.OptionSubscribe, "")
			if err != nil {
				log.Printf("could not subscribe to topic %v", err)
			}
			fmt.Printf("subscribe\n")
			time.Sleep(time.Second)
		}
	}()

	pub := zmq4.NewPub(ctx)
	err = pub.Dial("tcp://*:1234")
	if err != nil {
		log.Fatalf("could not dial: %v", err)
	}
	for {
		msg := zmq4.NewMsgString("test abc")
		err := pub.Send(msg)
		if err != nil {
			log.Printf("could send message: %v", err)
		}
		fmt.Printf("msg send\n")
		time.Sleep(time.Second)
	}