Simple Golang SSE example using CloseNotifier

sse.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"time"
)

// SSE writes Server-Sent Events to an HTTP client.
type SSE struct{}

var messages = make(chan string)

func (s *SSE) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
	f, ok := rw.(http.Flusher)
	if !ok {
		http.Error(rw, "cannot stream", http.StatusInternalServerError)
		return
	}

	rw.Header().Set("Content-Type", "text/event-stream")
	rw.Header().Set("Cache-Control", "no-cache")
	rw.Header().Set("Connection", "keep-alive")

	cn, ok := rw.(http.CloseNotifier)
	if !ok {
		http.Error(rw, "cannot stream", http.StatusInternalServerError)
		return
	}

	for {
		select {
		case <-cn.CloseNotify():
			log.Println("done: closed connection")
			return
		case msg := <-messages:
			fmt.Fprintf(rw, "data: %s\n\n", msg)
			f.Flush()
		}
	}
}

func main() {
	http.Handle("/", &SSE{})

	go func() {
		for i := 0; i < 10; i++ {
			messages <- "yo"
			time.Sleep(time.Second)
		}
	}()

	log.Fatal(http.ListenAndServe(":3000", nil))
}