使用GoRoute和ShellRoute处理路由的最佳方法是什么？
我有3个屏幕。设置-显示全屏A -显示底部导航（用 shell 路线包裹）B -显示底部导航（用 shell 路线包裹）
我在这个配置中遇到的唯一问题是当我进入设置屏幕时缺少一个后退按钮。我该如何修复它？

final goRouter = GoRouter(
  initialLocation: '/a',
  navigatorKey: _rootNavigatorKey,
  routes: [
    GoRoute( // = Do not show Bottom Navigation, just a full screen
      path: '/settings',
      pageBuilder: (context, state) => const NoTransitionPage(
        child: SettingsPage(),
      ),
    ),
    ShellRoute( // ShellRoute = Show Bottom Navigation
      navigatorKey: _shellNavigatorKey,
      builder: (context, state, child) {
        return ScaffoldWithBottomNavigation(
          tabs: tabs,
          child: child,
        );
      },
      routes: [
        GoRoute( 
          path: '/a',
          pageBuilder: (context, state) => const NoTransitionPage(
            child: HomeScreen(label: 'A', detailsPath: '/a/details'),
          ),
          routes: [
            GoRoute(
              path: 'details',
              builder: (context, state) => const DetailsScreen(label: 'A'),
            ),
          ],
        ),
        GoRoute(
          path: '/b',
          pageBuilder: (context, state) => const NoTransitionPage(
            child: HomeScreen(label: 'B', detailsPath: '/b/details'),
          ),
          routes: [
            GoRoute(
              path: 'details',
              builder: (context, state) => const DetailsScreen(label: 'B'),
            ),
          ],
        ),
      ],
    ),
  ],
);