final dio = Dio();
final dir = await getApplicationSupportDirectory();
final cookieJar = PersistCookieJar(storage: FileStorage(join(dir.path, "cookies")));
dio.interceptors.add(CookieManager(cookieJar));
dio.get("http://site1") ; // This is a 302 redirect url. The redirected site2 url will return the set-cookie response header

  Future<void> _saveCookies(Response response) async {
    final setCookies = response.headers[HttpHeaders.setCookieHeader];

    if (setCookies != null) {
      final cookies = setCookies
          .map((str) => str.split(_setCookieReg))
          .expand((element) => element);
      await cookieJar.saveFromResponse(
        response.requestOptions.uri, // Should this be changed to response.realUri ?
        cookies.map((str) => Cookie.fromSetCookieValue(str)).toList(),
      );
    }
  }