Url path not changing when navigating back to previous page in flutter web

I am working on a flutter app. i have set up router in the app with named routes. on going to my home page it shows as locahost:1234/#/home. and the path is correct. but from there when a navigate back to previouse page it still showing the same path locahost:1234/#/home. the path url is not changing on navigating back. if any one has an idea? my router file is as follows:

  /* ADD REPOSITORY TO APP ROUTER */
  /* ADD REPOSITORY TO APP ROUTER */
  Repository repository;
  AppRouter() {
    repository = new Repository(apiService: ApiService());
  }

  Route generateRoute(RouteSettings settings) {
    switch (settings.name) {
      case "/":
        return MaterialPageRoute(
          settings: RouteSettings(name: '/'),
            builder: (_) => MultiBlocProvider(providers: [
                  BlocProvider<HomeCubit>(
                    create: (BuildContext context) {
                      return HomeCubit(repository: repository);
                    },
                  ),
                  BlocProvider<SearchCubit>(
                    create: (BuildContext context) =>
                        SearchCubit(repository: repository),
                  ),
                  BlocProvider<UserCubit>(
                    create: (BuildContext context) {
                      return UserCubit(repository: repository);
                    },
                  )
                ], child:userToken==null?SplashScreen():NavScreen()
                // SplashScreen()
                ));
                case "/getstarted":
                 return MaterialPageRoute(
           settings: RouteSettings(name: '/getstarted'),
            builder: (_) => BlocProvider(
                create: (BuildContext context) =>
                    ProfileCubit(repository: repository),
                child: OnboardingScreen()));
      //return MaterialPageRoute(builder: (_) => VideoDetailScreen());
      case "/register":
        return MaterialPageRoute(
           settings: RouteSettings(name: '/register'),
            builder: (_) => MultiBlocProvider(providers: [
                  BlocProvider<HomeCubit>(
                    create: (BuildContext context) {
                      return HomeCubit(repository: repository);
                    },
                  ),
                  BlocProvider<SearchCubit>(
                    create: (BuildContext context) =>
                        SearchCubit(repository: repository),
                  ),
                  BlocProvider<UserCubit>(
                    create: (BuildContext context) =>
                        UserCubit(repository: repository),
                  )
                ], child: RegisterScreen()));
      case '/home':
        return MaterialPageRoute(
           settings: RouteSettings(name: '/home'),
            builder: (_) => BlocProvider(
                create: (BuildContext context) =>
                    HomeCubit(repository: repository),
                child: NavScreen()));
      case '/signin':
        return MaterialPageRoute(
            builder: (_) => BlocProvider(
                create: (BuildContext context) =>
                    UserCubit(repository: repository),
                child: SigninScreen()),
                 settings: RouteSettings(name: '/signin'));
      default:
        return MaterialPageRoute(builder: (_) {
          return Scaffold(
            body: Center(
              child: Text('Error! No route Found...',
              style: TextStyle(color: Colors.white,fontWeight:FontWeight.bold),),
            ),
          );
        }
        );
    }
  }
}