feat(go): add load simulator hold mode

go/vehicle-gateway/internal/loadsim/runner_test.go

@@ -34,6 +34,7 @@ func TestRunnerDialsTargetConnectionsAndWritesFrames(t *testing.T) {
 		SendInterval:         time.Millisecond,
 		Duration:             5 * time.Millisecond,
 		Template:             "0200",
+		SendFrames:           true,
 	})
 	if err != nil {
 		t.Fatalf("Run() error = %v", err)
@@ -53,6 +54,41 @@ func TestRunnerDialsTargetConnectionsAndWritesFrames(t *testing.T) {
 	}
 }
 
+func TestRunnerCanHoldConnectionsWithoutWritingFrames(t *testing.T) {
+	var writes atomic.Int64
+	runner := Runner{
+		Dial: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			return &recordingConn{
+				write: func(p []byte) (int, error) {
+					writes.Add(1)
+					return len(p), nil
+				},
+				close: func() error { return nil },
+			}, nil
+		},
+	}
+
+	stats, err := runner.Run(context.Background(), Config{
+		Protocol:             ProtocolJT808,
+		Addr:                 "127.0.0.1:808",
+		Connections:          2,
+		ConnectRatePerSecond: 1000,
+		SendInterval:         time.Millisecond,
+		Duration:             5 * time.Millisecond,
+		Template:             "0200",
+		SendFrames:           false,
+	})
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if stats.ConnectionsOpened != 2 {
+		t.Fatalf("ConnectionsOpened = %d, want 2", stats.ConnectionsOpened)
+	}
+	if stats.FramesWritten != 0 || writes.Load() != 0 {
+		t.Fatalf("frames written stats=%d writes=%d, want 0", stats.FramesWritten, writes.Load())
+	}
+}
+
 type recordingConn struct {
 	write func([]byte) (int, error)
 	close func() error