server.go

package main

import (
	"fmt"
	"net/http"
)

func broadcaster(in chan chan string, out chan chan string, listen chan string) {
	chans := map[chan string]bool{}
	for {
		select {
		case ch := <-in:
			chans[ch] = true
		case ch := <-out:
			delete(chans, ch)
		case s := <-listen:
			for ch := range chans {
				ch <- s
			}
		}
	}
}

var (
	subscribe	= make(chan chan string)
	unsubscribe	= make(chan chan string)
	publish		= make(chan string)
)

func init() {
	go broadcaster(subscribe, unsubscribe, publish)
}

func home(w http.ResponseWriter, r *http.Request) {
	ch := make(chan string)
	subscribe <- ch
	defer func() {
		unsubscribe <- ch
	}()

	fmt.Fprintln(w, <-ch)
}

func send(w http.ResponseWriter, r *http.Request) {
	publish <- r.FormValue("msg")
	fmt.Fprintln(w, "Sent!")
}

func main() {
	http.HandleFunc("/", home)
	http.HandleFunc("/send", send)

	fmt.Println("Running at http://localhost:8080")
	http.ListenAndServe(":8080", nil)
}