feat: implement stale client removal after timeout

- add goroutine to remove stale clients from the connection pool
- update client struct to track `LastPong` time
- set write deadline for websocket connections
- move package variables and const to `vars.go`
- log additional information when broadcasting errors

🤖

internal/websocket/staleClients.go

@@ -0,0 +1,34 @@
+package websocket
+
+import (
+	"time"
+
+	"git.smsvc.net/pomodoro/GoTomato/internal/helper"
+	"git.smsvc.net/pomodoro/GoTomato/pkg/models"
+	"github.com/gorilla/websocket"
+)
+
+// Check and remove stale clients
+func RemoveStaleClients() {
+	ticker := time.NewTicker(STALE_CHECK_INTERVALL * time.Second)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		mu.Lock()
+		for _, client := range Clients {
+			client.Conn.SetWriteDeadline(time.Now().Add(SEND_TIMEOUT * time.Second))
+			client.Conn.WriteMessage(websocket.PingMessage, nil)
+
+			if isStale(client) {
+				helper.Logger.Info("Removing stale client", "host", client.RealIP, "lastPong", client.LastPong.Format(time.RFC3339))
+				client.Conn.Close()
+				delete(Clients, client.Conn.LocalAddr())
+			}
+		}
+		mu.Unlock()
+	}
+}
+
+func isStale(client *models.WebsocketClient) bool {
+	return time.Since(client.LastPong) > (STALE_CLIENT_TIMEOUT * time.Second)
+}