go-sse

Server-Sent Events for Go

About

Server-sent events is a method of continuously sending data from a server to the browser, rather than repeatedly requesting it, replacing the "long polling way".

It's supported by all major browsers and for IE/Edge you can use a polyfill.

go-sse is a small library to create a Server-Sent Events server in Go and works with Go 1.6+.

Features

• Multiple channels (isolated)
• Broadcast message to all channels
• Custom headers (useful for CORS)
• Last-Event-ID support (resend lost messages)
• Follow SSE specification

Getting Started

Simple Go example that handle 2 channels and send messages to all clients connected in each channel.

package main

import (
    "log"
    "net/http"
    "strconv"
    "time"

    "github.com/alexandrevicenzi/go-sse"
)

func main() {
    // Create the server.
    s := sse.NewServer(nil)
    defer s.Shutdown()

    // Register with /events endpoint.
    http.Handle("/events/", s)

    // Dispatch messages to channel-1.
    go func () {
        for {
            s.SendMessage("/events/channel-1", sse.SimpleMessage(time.Now().String()))
            time.Sleep(5 * time.Second)
        }
    }()

    // Dispatch messages to channel-2
    go func () {
        i := 0
        for {
            i++
            s.SendMessage("/events/channel-2", sse.SimpleMessage(strconv.Itoa(i)))
            time.Sleep(5 * time.Second)
        }
    }()

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

Connecting to our server from JavaScript:

e1 = new EventSource('/events/channel-1');
e1.onmessage = function(event) {
    // do something...
};

e2 = new EventSource('/events/channel-2');
e2.onmessage = function(event) {
    // do something...
};