oauth: automatically clean up expired oauth state in db

main.go

@@ -48,13 +48,17 @@ func runApp(ctx context.Context) error {
 		return fmt.Errorf("failed to initialize database connection pool: %w", err)
 	}
 
-	// start http server
+	// start background processes
 
 	auth, err := authentication.New(ctx, connPool)
 	if err != nil {
 		return fmt.Errorf("failed to construct authenticator: %w", err)
 	}
 
+	authErrCh := runAuthProcesses(ctx, auth)
+
+	// start http server
+
 	srvErrCh := runServer(ctx, connPool, auth)
 
 	// wait for interrupt signal or unrecoverable failure, then shutdown
@@ -62,13 +66,24 @@ func runApp(ctx context.Context) error {
 	osSignalCh := make(chan os.Signal, 1)
 	signal.Notify(osSignalCh, syscall.SIGINT, syscall.SIGTERM)
 
-	var serverAlreadyShutdown bool
+	var (
+		alreadyShutdown struct {
+			server        bool
+			authProcesses bool
+		}
+	)
 	select {
 	case s := <-osSignalCh:
 		fmt.Println("application received shutdown signal:", s)
 		fmt.Println("shutting down")
+	case err := <-authErrCh:
+		alreadyShutdown.authProcesses = true
+		fmt.Println("auth processes shutdown unexpectedly")
+		if err != nil {
+			fmt.Println("auth processes encountered error:", err)
+		}
 	case err := <-srvErrCh:
-		serverAlreadyShutdown = true
+		alreadyShutdown.server = true
 		fmt.Println("server shutdown unexpectedly")
 		if err != nil {
 			fmt.Println("server encountered error:", err)
@@ -81,7 +96,14 @@ func runApp(ctx context.Context) error {
 
 	var errs []error
 
-	if !serverAlreadyShutdown {
+	if !alreadyShutdown.authProcesses {
+		if err := <-authErrCh; err != nil {
+			errs = append(errs, fmt.Errorf("auth processes experienced an error: %w", err))
+		}
+		fmt.Println("auth processes shut down")
+	}
+
+	if !alreadyShutdown.server {
 		if err := <-srvErrCh; err != nil {
 			errs = append(errs, fmt.Errorf("server experienced an error: %w", err))
 		}
@@ -91,6 +113,19 @@ func runApp(ctx context.Context) error {
 	return errors.Join(errs...)
 }
 
+func runAuthProcesses(ctx context.Context, auth *authentication.Authenticator) <-chan error {
+	errCh := make(chan error, 1)
+	go func() {
+		defer close(errCh)
+
+		if err := auth.RunBackgroundCleanup(ctx); err != nil {
+			errCh <- err
+		}
+	}()
+
+	return errCh
+}
+
 func runServer(ctx context.Context, connPool *pgxpool.Pool, auth *authentication.Authenticator) <-chan error {
 	srv := &http.Server{
 		Addr:    ":8082", // local