Fixed lint issues and missing documentation

cmd/mock-fts/main.go

@@ -191,7 +191,7 @@ func (o *options) validate() error {
 }
 
 // run starts the mock and blocks until ctx is cancelled or the server fails.
-func run(ctx context.Context, o *options) error {
+func run(ctx context.Context, o *options) (err error) {
 	loc, err := time.LoadLocation(o.tz) // already validated
 	if err != nil {
 		return fmt.Errorf("--tz: %w", err)
@@ -228,7 +228,7 @@ func run(ctx context.Context, o *options) error {
 	if err != nil {
 		return err
 	}
-	defer store.Close()
+	defer func() { err = errors.Join(err, store.Close()) }()
 
 	// ----- generator -----
 	gen := mock.NewGenerator(cat, store, time.Now().UnixNano())
@@ -261,7 +261,7 @@ func run(ctx context.Context, o *options) error {
 			<-workerDone
 			return fmt.Errorf("opening access log: %w", err)
 		}
-		defer f.Close()
+		defer func() { err = errors.Join(err, f.Close()) }()
 		out = f
 	}
 	accessLogger := log.New(out, "", 0)
@@ -279,11 +279,14 @@ func run(ctx context.Context, o *options) error {
 	}
 	go func() {
 		<-ctx.Done()
+		// ctx is done by now; the shutdown gets its own deadline.
 		shutdownCtx, cancelShutdown := context.WithTimeout(
-			context.Background(), 5*time.Second,
+			context.WithoutCancel(ctx), 5*time.Second,
 		)
 		defer cancelShutdown()
-		httpSrv.Shutdown(shutdownCtx)
+		if err := httpSrv.Shutdown(shutdownCtx); err != nil {
+			log.Printf("shutdown: %v", err)
+		}
 	}()
 
 	log.Printf("FTS mock listening on %s%s (query times in %s)", o.addr, mock.BasePath, loc)