fix: correct issues with running http and asynq in parallel

Signed-off-by: Janne Mareike Koschinski <janne@kuschku.de>

backend/main.go

@@ -53,14 +53,15 @@ func main() {
 		Handler: metricsMux,
 	}
 
-	go func() {
+	runner := shared.Runner{}
+	runner.RunParallel(func() {
 		if err := metrics.ListenAndServe(); err != nil && err != http.ErrServerClosed {
 			log.Printf("error in metrics server: %s", err.Error())
 		}
 		log.Printf("metrics shut down, shutting down asynq as well")
 		srv.Shutdown()
-	}()
-	go func() {
+	})
+	runner.RunParallel(func() {
 		if err := srv.Run(mux); err != nil {
 			log.Printf("error in asynq server: %s", err.Error())
 		}
@@ -68,5 +69,6 @@ func main() {
 		if err := metrics.Shutdown(context.Background()); err != nil {
 			log.Printf("error shutting down metrics server: %s", err.Error())
 		}
-	}()
+	})
+	runner.Wait()
 }

shared/runner.go

+package shared
+
+import "sync"
+
+type Runner struct {
+	wg sync.WaitGroup
+}
+
+func (runner *Runner) RunParallel(closure func()) {
+	runner.wg.Add(1)
+	go func() {
+		closure()
+		runner.wg.Done()
+	}()
+}
+
+func (runner *Runner) Wait() {
+	runner.wg.Wait()
+}