Websocket handling

handler.go

func (h *HTTPAdapter) Socket(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
	conn, err := socketUpgrader.Upgrade(w, r, http.Header{})
	if err != nil {
		http.Error(w, "Socket could not be established", http.StatusExpectationFailed)
		return
	}
	h.switchboard.Connect(h.topic, conn)

	conn.SetCloseHandler(func(code int, text string) error {
		h.switchboard.Disconnect(h.topic, conn)
		_ = conn.Close()
		return nil
	})
	for {
		_, _, err := conn.ReadMessage()
		if err != nil {
			return
		}
	}
}

swtichboard.go

package main

import (
	"sync"
	"time"
)

type JSONWriter interface {
	WriteJSON(v interface{}) error
}
type Broadcaster interface {
	Broadcast(Recordable)
	Receive(func(Message))
}

type Channel struct {
	connections sync.Map
}

func NewChannel() *Channel {
	return &Channel{}
}

func (c *Channel) Connect(conn JSONWriter) {
	c.connections.Store(conn, struct{}{})
}

func (c *Channel) Disconnect(conn JSONWriter) {
	c.connections.Delete(conn)
}

func (c *Channel) Broadcast(data interface{}) {
	c.connections.Range(func(key, _ interface{}) bool {
		_ = key.(JSONWriter).WriteJSON(data)
		return true
	})
}

type Switchboard struct {
	channels sync.Map
}

func NewSwitchboard() *Switchboard {
	switchboard := &Switchboard{}
	go switchboard.KeepAlive()
	return switchboard
}

func (s *Switchboard) Connect(key string, conn JSONWriter) {
	s.channel(key).Connect(conn)
}

func (s *Switchboard) channel(key string) *Channel {
	c, _ := s.channels.LoadOrStore(key, NewChannel())
	return c.(*Channel)
}

func (s *Switchboard) Disconnect(key string, conn JSONWriter) {
	s.channel(key).Disconnect(conn)
}

func (s *Switchboard) Broadcast(key string, data interface{}) {
	s.channel(key).Broadcast(data)
}

func (s *Switchboard) KeepAlive() {
	for {
		select {
		case <-time.After(45 * time.Second):
			s.channels.Range(func(_, channel interface{}) bool {
				channel.(*Channel).Broadcast(
					map[string]string{
						"topic": "PING",
						"time":  time.Now().Format(time.RFC3339),
					})
				return true
			})
		}
	}
}