Pub/Sub Pattern Golang

main.go

package main

import (
	"patternsample/mq"
	"fmt"
	"time"
)

func main() {

	// New
	mque := mq.New()

	// Subscribe topic
	mque.Subscribe("Notify", func(m *mq.Message) {
		fmt.Println("Received, Topic: Notify")
	})

	// Subscribe topic
	mque.Subscribe("Test2", func(m *mq.Message) {
		fmt.Println("Received, Topic: Test2")
	})

	// Publish value into topic
	mque.Publish(
		mq.Message{
			Topic: "Notify",
			Value: "blablabla",
		},
	)

	// ;)
	time.Sleep(2 * time.Second)

	// Publish value into topic
	mque.Publish(
		mq.Message{
			Topic: "Test2",
			Value: "blablabla",
		},
	)

	// Publish value into topic
	mque.Publish(
		mq.Message{
			Topic: "NotFound",
			Value: "blablabla",
		},
	)

	// ;)
	time.Sleep(1 * time.Second)

}

mq.go

package mq

import "errors"

//Message struct
type Message struct {
	Topic string
	Value interface{}
}

//Channel struct
type Channel struct {
	ch chan Message
}

//Mq struct
type Mq struct {
	topics map[string]*Channel
}

// var sessions map[string][]Session

//New func
func New() *Mq {
	return &Mq{
		topics: map[string]*Channel{},
	}
}

//Subscribe method
func (s *Mq) Subscribe(topic string, handler func(m *Message)) error {

	// generate topic if not exist
	if _, exist := s.topics[topic]; exist {
		//TODO: make Session List for handle multiple Subscribe on Single Topic
		return errors.New(("Subscribe exist, topic:" + topic))
	}

	s.topics[topic] = &Channel{
		ch: make(chan Message),
	}

	go func() {
		for {
			c := <-s.topics[topic].ch
			handler(&c)
		}
	}()
	return nil
}

//Publish method
func (s *Mq) Publish(msg Message) error {
	if _, ok := s.topics[msg.Topic]; !ok {
		return errors.New("Topic has been closed")
	}

	s.topics[msg.Topic].ch <- msg

	return nil
}

Per Subscribe Topic ~> Generate Single Channel.
You can not subscribe topic more than once

if you want to has multiple subscribe on a Topic, Create Subscribe List and publish on each session (Per Subscribe -> Channel) (FanOut)

so informative