Golang PubSub

pubsub.go

package pubsub

import (
	"reflect"
	"sync"
)

// PubSub system.
type PubSub interface {
	// Pub publishes to the given topic.
	Pub(topic string, v interface{})
	// Sub subscribes the channel to the given topic.
	Sub(topic string, ch interface{}) (unsub func())
}

type pubSub struct {
	clients sync.Map
}

type client struct {
	topic string
	chVal reflect.Value
}

// New creates a PubSub implementation.
func New() PubSub {
	return new(pubSub)
}

func (ps *pubSub) Pub(topic string, v interface{}) {
	val := reflect.ValueOf(v)
	ps.clients.Range(func(key, _ interface{}) bool {
		c := key.(*client)

		if c.topic == topic {
			c.chVal.Send(val)
		}

		return true
	})
}

func (ps *pubSub) Sub(topic string, ch interface{}) func() {
	chVal := reflect.ValueOf(ch)

	if chVal.Kind() != reflect.Chan {
		panic("pubsub: ch is the wrong type")
	}

	c := &client{topic, chVal}
	ps.clients.Store(c, nil)

	return func() {
		ps.clients.Delete(c)
	}
}

Ex:

func main() {
	ps := pubsub.New()

	events := make(chan string)
	defer close(events)
	defer ps.Sub("events", events)()

	var wg sync.WaitGroup
	wg.Add(2)

	go func() {
		defer wg.Done()
		ps.Pub("events", "hello there")
	}()

	go func() {
		defer wg.Done()
		fmt.Println("event:", <-events)
	}()

	wg.Wait()
}