startLocale not work

[mhkarami]

this is my code :

  WidgetsFlutterBinding.ensureInitialized();
  await EasyLocalization.ensureInitialized();
...
  runApp(EasyLocalization(
    supportedLocales: const [ENGLISH_LOCALE, PERSIAN_LOCALE],
    path: ASSETS_PATH_LOCALISATIONS,
    fallbackLocale: ENGLISH_LOCALE,
    // startLocale: PERSIAN_LOCALE,
    startLocale: ENGLISH_LOCALE,
    saveLocale: true,
    child: MyApp(),
  ));

class MyApp extends StatelessWidget {
  ...
  @override
  Widget build(BuildContext context) {
    return GlobalProvider(
      child: MaterialApp.router(
        routerConfig: _appRouter.config(),
        locale: context.locale,
        supportedLocales: context.supportedLocales,
        localizationsDelegates: context.localizationDelegates,
        scaffoldMessengerKey: Constants.skaffoldMessengerStateKey,

const String ASSETS_PATH_LOCALISATIONS = "assets/translations";
const Locale PERSIAN_LOCALE = Locale("fa","IR");
const Locale ENGLISH_LOCALE = Locale("en","US");

startLocale not work truly .
some question that asked in stackoverflow with same problem
flutter easy_localization 3.0.2 - default language at boot
How I can set the default language in flutter using easy localization?

also there is a strange behavior :
when i set saveLocale: true app starts with PERSIAN_LOCALE and when i set saveLocale: false app starts with ENGLISH_LOCALE.