fix: prevent user starting wails app twice (#709)

Fixes #467

The simplest change to prevent Alby Hub running twice in Wails mode
which could potentially cause corruption of the LDK directory. This is
equivalent to how the http mode prevents it, but even better because the
port is allocated even before the service starts.

main_wails.go

@@ -6,6 +6,7 @@ package main
 import (
 	"context"
 	"embed"
+	"net"
 
 	"github.com/getAlby/hub/logger"
 	"github.com/getAlby/hub/service"
@@ -20,6 +21,14 @@ var assets embed.FS
 var appIcon []byte
 
 func main() {
+	// Get a port lock on a rare port to prevent the app running twice
+	listener, err := net.Listen("tcp", "0.0.0.0:21420")
+	if err != nil {
+		log.Println("Another instance of Alby Hub is already running.")
+		return
+	}
+	defer listener.Close()
+
 	log.Info("Alby Hub starting in WAILS mode")
 	ctx, cancel := context.WithCancel(context.Background())
 	svc, _ := service.NewService(ctx)