chore: use os.Stdout instead of t.Output() (#8860)

Signed-off-by: zirain <zirain2009@gmail.com>

Author: zirain

internal/cmd/server_runner_race_test.go

@@ -20,40 +20,41 @@ import (
 	"github.com/envoyproxy/gateway/internal/logging"
 )
 
-// TestRunnerGoroutineRace specifically reproduces the data race from CI by
-// simulating the exact condition: goroutines logging while test cleanup closes t.Output()
+// TestRunnerGoroutineRace tests that background goroutines can safely log after context cancellation.
+// This test previously exposed a data race when using t.Output() - the test would complete and
+// close t.Output() while background goroutines were still logging. The fix is to use os.Stdout
+// instead, which is thread-safe and remains valid after the test completes.
 //
-// The race happens because runner.Close() is a no-op - it returns immediately
-// without waiting for goroutines to finish. When the test ends, cleanup closes
-// t.Output() while goroutines are still active.
+// Note: In production, certGen is called with cmd.OutOrStdout() which resolves to os.Stdout
+// in most cases, so using os.Stdout in tests mirrors real-world behavior.
 //
 // Run with: go test -race -run TestRunnerGoroutineRace -count=100 ./internal/cmd/
 func TestRunnerGoroutineRace(t *testing.T) {
 	// Skip if not running with race detector
-	// This test is specifically designed to catch the race
 	if !testing.Short() {
-		t.Skip("Run with -race flag to detect the race")
+		t.Skip("Run with -race flag to verify no race conditions")
 	}
 
 	configHome := t.TempDir()
 	cfgFileContent := strings.ReplaceAll(fileProviderGatewayConfig, "[CONFIG_HOME_PLACE_HODLER]", configHome)
 	configPath := path.Join(t.TempDir(), "envoy-gateway.yaml")
 	require.NoError(t, os.WriteFile(configPath, []byte(cfgFileContent), 0o600))
 
-	require.NoError(t, certGen(t.Context(), t.Output(), true, configHome))
+	require.NoError(t, certGen(t.Context(), os.Stdout, true, configHome))
 
 	// Use a context WITHOUT defer cancel to keep goroutines alive longer
 	ctx, cancel := context.WithCancel(context.Background())
 
 	hook := func(c context.Context, cfg *config.Server) error {
-		cfg.Logger = logging.DefaultLogger(t.Output(), egv1a1.LogLevelInfo)
+		// Use os.Stdout instead of t.Output() - it's thread-safe and won't cause races
+		cfg.Logger = logging.DefaultLogger(os.Stdout, egv1a1.LogLevelInfo)
 		return startRunners(c, cfg, nil)
 	}
 
 	errCh := make(chan error, 1)
 
 	go func() {
-		errCh <- server(ctx, t.Output(), t.Output(), configPath, hook, nil)
+		errCh <- server(ctx, os.Stdout, os.Stdout, configPath, hook, nil)
 	}()
 
 	// Let runners start and become active
@@ -62,19 +63,13 @@ func TestRunnerGoroutineRace(t *testing.T) {
 	// Cancel context - triggers shutdown but goroutines may still be logging
 	cancel()
 
-	// Don't wait for server to complete - this creates the race!
-	// Test will end, cleanup will close t.Output(), while goroutines
-	// are still running and trying to log
+	// Wait briefly to see if server completes or if goroutines are still running
 	select {
 	case <-errCh:
-		// Server finished
+		// Server finished cleanly
 	case <-time.After(20 * time.Millisecond):
-		// Timeout - goroutines likely still running
-		// Test ends here, cleanup starts -> RACE!
+		// Server still running - this is fine with os.Stdout (no race)
 	}
-
-	// Test ends immediately - race window is NOW
-	// Without fix: goroutines still running, trying to log to closed t.Output()
 }
 
 // TestRunnerGoroutineRaceStress runs multiple quick cycles to maximize
@@ -87,20 +82,21 @@ func TestRunnerGoroutineRaceStress(t *testing.T) {
 			configPath := path.Join(t.TempDir(), "envoy-gateway.yaml")
 			require.NoError(t, os.WriteFile(configPath, []byte(cfgFileContent), 0o600))
 
-			require.NoError(t, certGen(t.Context(), t.Output(), true, configHome))
+			require.NoError(t, certGen(t.Context(), os.Stdout, true, configHome))
 
 			ctx, cancel := context.WithCancel(context.Background())
 			defer cancel()
 
 			hook := func(c context.Context, cfg *config.Server) error {
-				cfg.Logger = logging.DefaultLogger(t.Output(), egv1a1.LogLevelInfo)
+				// Use os.Stdout instead of t.Output() - it's thread-safe and won't cause races
+				cfg.Logger = logging.DefaultLogger(os.Stdout, egv1a1.LogLevelInfo)
 				return startRunners(c, cfg, nil)
 			}
 
 			errCh := make(chan error, 1)
 
 			go func() {
-				errCh <- server(ctx, t.Output(), t.Output(), configPath, hook, nil)
+				errCh <- server(ctx, os.Stdout, os.Stdout, configPath, hook, nil)
 			}()
 
 			// Vary timing to hit different race windows
@@ -111,8 +107,6 @@ func TestRunnerGoroutineRaceStress(t *testing.T) {
 
 			err := <-errCh
 			require.NoError(t, err)
-
-			// Race window: goroutines may still be logging
 		})
 	}
 }