Publish–subscribe in Go

gistfile1.go

package main

import (
	"fmt"
	"sync"
	"time"
)

type Publisher struct {
	mutex       sync.RWMutex
	subscribers map[chan<- interface{}]bool
	closed      bool
}

func New() *Publisher {
	return &Publisher{
		subscribers: make(map[chan<- interface{}]bool),
		closed:      false,
	}
}

func (p *Publisher) Close() {
	p.mutex.Lock()
	defer p.mutex.Unlock()
	for subscriber := range p.subscribers {
		close(subscriber)
	}
	p.closed = true
}

func (p *Publisher) Publish(value interface{}) {
	p.mutex.RLock()
	defer p.mutex.RUnlock()
	if p.closed {
		panic("publish on closed publisher")
	}
	for subscriber := range p.subscribers {
		subscriber <- value
	}
}

func (p *Publisher) Subscribe(s chan<- interface{}) {
	p.mutex.Lock()
	defer p.mutex.Unlock()
	p.subscribers[s] = true
}

func (p *Publisher) Unsubscribe(s chan<- interface{}) {
	p.mutex.Lock()
	defer p.mutex.Unlock()
	delete(p.subscribers, s)
}

func main() {
	publisher := New()
	for i := 0; i < 5; i++ {
		go func() {
			c := make(chan interface{})
			publisher.Subscribe(c)
			defer publisher.Unsubscribe(c)
			for x := range c {
				fmt.Println(x.(int))
			}
			fmt.Println("done!")
		}()
	}
	time.Sleep(time.Second)
	for i := 0; i < 5; i++ {
		publisher.Publish(i)
	}
	publisher.Close()
	time.Sleep(time.Second)
}