Symfony redirect from "/" to "/{locale}" - symfony

Question

I am working on a Symfony(4.4) project. I am trying to make eventSubscriber that will redirect user with locale based on saved cookie. The idea is when I visit homepage for first time(or if I have not saved cookie) I have to redirect myself to homepage with the default locale(which is 'en' in my case). When I change the locale I save the new locale in cookie (for example my cookie is "LOCALE" => 'de'). When I enter in homepage next time I have to redirect myself with the 'de' locale(because it's saved on the cookie). When I set the priority to 32+ I get redirect to the default locale instead the cookie locale(I receive the cookie content, so the problem is not from the cookie), else if I set the priority before 32 I get the error "Route not found for '/' " https://imgur.com/0YAtgqs. For now I made this:
I added new method in RequestSubscriber:
public function redirectToCookieLocale(RequestEvent $event)
{
if ($event->isMasterRequest() === false) {
return;
}
$request = $event->getRequest();
$path = $event->getRequest()->getPathInfo();
$cookieLocale = $request->cookies->get('LOCALE');
if ($cookieLocale != null && $this->isValidLocale($cookieLocale)) {
$locale = $request->cookies->get('LOCALE');
} else {
$locale = $request->getDefaultLocale();
}
if ($path == '/') {
$event->setResponse(new RedirectResponse(
$this->generator->generate(
'frontend_index',
['_locale' => $locale]
),
301
));
}
}
public static function getSubscribedEvents(): array
{
return [
KernelEvents::REQUEST => [
['redirectToCookieLocale', 30]
]
];
}
Also I created ResponseSubscriber where I create the cookie:
public function onKernelResponse(ResponseEvent $event)
{
$request = $event->getRequest();
$response = $event->getResponse();
if ($response->isRedirection()) {
return;
}
$urlLocale = $request->get('_locale');
$cookieLocale = $request->cookies->get('LOCALE');
if ($urlLocale != null && $urlLocale != $cookieLocale) {
$cookie = new Cookie('LOCALE', $request->getLocale(), (time() + 3600 * 24 * 7), '/', '', '', false);
$response->headers->setCookie($cookie);
}
}
public static function getSubscribedEvents(): array
{
return [
KernelEvents::RESPONSE => [
['onKernelResponse', 0],
],
];
}