A sample server sent event with golang

sse.go

package main

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/go-chi/chi"
	"github.com/sirupsen/logrus"
	"golang.org/x/sync/errgroup"
)

var pingInterval = time.Second * 10

// HandleLiveLog returns an http.HandlerFunc that processes an http.Request
// to server sent event.
func HandleLiveLog() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		ctx := r.Context()
		h := w.Header()
		h.Set("Content-Type", "text/event-stream")
		h.Set("Cache-Control", "no-cache")
		h.Set("Connection", "keep-alive")
		h.Set("X-Accel-Buffering", "no")

		f, ok := w.(http.Flusher)
		if !ok {
			return
		}

		io.WriteString(w, ": ping\n\n")
		f.Flush()
	L:
		for {
			select {
			case <-ctx.Done():
				logrus.Info("events: stream cancelled")
				break L
			case <-time.After(pingInterval):
				io.WriteString(w, ": heart beat\n\n")
				f.Flush()
			default:
				fmt.Fprintf(w, "%s\n", time.Now().Format(time.RFC1123))
				f.Flush()
				time.Sleep(2 * time.Second)
			}
		}

		io.WriteString(w, "event: error\ndata: eof\n\n")
		f.Flush()

		logrus.Info("events: stream closed")

	}
}

func main() {

	r := chi.NewRouter()
	r.Get("/livelog", HandleLiveLog())
	srv := &http.Server{
		Addr:        ":4343",
		ReadTimeout: 75 * time.Second,
		Handler:     r,
	}

	ctx, cancel := context.WithCancel(context.Background())
	go func() {
		c := make(chan os.Signal, 1)
		signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
		defer signal.Stop(c)

		select {
		case <-ctx.Done():
		case <-c:
			cancel()
		}
	}()
	var g errgroup.Group

	g.Go(func() error {
		return srv.ListenAndServe()
	})

	g.Go(func() error {
		<-ctx.Done()
		return srv.Shutdown(ctx)
	})

	if err := g.Wait(); err != nil {
		logrus.WithError(err).Info("shutdown server")
	}
}