func subscribe(t *testing.T, b broker.Broker, topic string, handle broker.Handler) broker.Subscriber {
s, err := b.Subscribe(topic, handle)
if err != nil {
t.Fatal(err)
}
return s
}
func publish(t *testing.T, b broker.Broker, topic string, msg *broker.Message) {
if err := b.Publish(topic, msg); err != nil {
t.Fatal(err)
}
}