Handle multiple display connections

Also drop the `quit` channel as we get good-enough signaling by closing the data channel.

main.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"sync"
 
 	"github.com/gorilla/websocket"
 )
@@ -18,8 +19,19 @@ var upgrader = websocket.Upgrader{
 	},
 }
 
+type client struct {
+	nudges chan [2]int
+	quit chan bool
+}
+
+type clientsStore struct {
+	set map[*client]struct{}
+	sync.RWMutex
+}
+
 func main() {
-	var nudges = make(chan [2]int)
+	var clients clientsStore
+	clients.set = make(map[*client]struct{})
 
 	go func() {
 		mux := http.NewServeMux()
@@ -45,7 +57,17 @@ func main() {
 					w.WriteHeader(http.StatusBadRequest)
 					return
 				}
-				nudges <- nudge
+				(func(){
+					clients.RLock()
+					defer clients.RUnlock()
+					for c, _ := range clients.set {
+						select {
+							case c.nudges <- nudge:
+							default:
+								log.Println("Client too slow -> dropping nudge")
+						}
+					}
+				})()
 				w.WriteHeader(http.StatusNoContent)
 			case "GET":
 				w.Header().Add("Content-Type", "text/html")
@@ -82,22 +104,29 @@ func main() {
 			log.Println(err)
 			return
 		}
-		var quit = make(chan bool)
+		defer con.Close()
+		var c client
+		c.nudges = make(chan [2]int)
+		(func() {
+			clients.Lock()
+			defer clients.Unlock()
+			clients.set[&c] = struct{}{}
+		})()
+		defer (func() {
+			clients.Lock()
+			defer clients.Unlock()
+			delete(clients.set, &c)
+			log.Println("Closing client connection")
+		})()
 		con.SetCloseHandler(func(code int, text string) error {
-			quit <- true
+			close(c.nudges)
 			return nil
 		})
-		for {
-			select {
-			case <-quit:
+		for n := range c.nudges {
+			err := con.WriteJSON(n)
+			if err != nil {
+				log.Println(err)
 				return
-			case n := <-nudges:
-				log.Println(n)
-				err := con.WriteJSON(n)
-				if err != nil {
-					log.Println(err)
-					return
-				}
 			}
 		}
 	})