fix lint errors detected by golangci-lint v2.11.4

Fix modernize issues in cmd/controller/main.go and a prealloc issue in
test/e2e/singlek8s/util.go.

Signed-off-by: Kohya Shiozaki <kouyan120706@gmail.com>

Author: skoya76

cmd/controller/main.go

@@ -410,12 +410,10 @@ func setupPrimary(ctx context.Context, mgr manager.Manager, wg *sync.WaitGroup)
 		return err
 	}
 
-	wg.Add(1)
-	go func() {
-		defer wg.Done()
+	wg.Go(func() {
 		<-ctx.Done()
 		_ = conn.Close()
-	}()
+	})
 
 	primarySettings := &controller.PrimarySettings{
 		ServiceEndpoint:        mantleServiceEndpoint,
@@ -467,22 +465,18 @@ func setupSecondary(ctx context.Context, mgr manager.Manager, wg *sync.WaitGroup
 		return fmt.Errorf("failed to listen %s: %w", mantleServiceEndpoint, err)
 	}
 
-	wg.Add(1)
-	go func() {
-		defer wg.Done()
+	wg.Go(func() {
 		err := serv.Serve(l)
 		if err != nil {
 			logger.Error(err, "gRPC server failed")
 		}
 		cancel()
-	}()
+	})
 
-	wg.Add(1)
-	go func() {
-		defer wg.Done()
+	wg.Go(func() {
 		<-ctx.Done()
 		serv.GracefulStop()
-	}()
+	})
 
 	return setupReconcilers(mgr, nil, &controller.SecondarySettings{
 		MaxImportJobs: maxImportJobs,

test/e2e/singlek8s/util.go

@@ -517,7 +517,9 @@ func getImageAndSnapNames(namespace, pool string) ([]string, error) {
 		}
 	}
 
-	return append(images, snaps...), nil
+	result := make([]string, 0, len(images)+len(snaps))
+
+	return append(append(result, images...), snaps...), nil
 }
 
 func checkJobExists(namespace, jobName string) (bool, error) {