fix route bug

com.unity.uiwidgets/Runtime/widgets/routes.cs

             _ModalScopeState scope = _scopeKey.currentState as _ModalScopeState ;
             D.assert(scope != null);
 
-            bool result = false;
-            foreach (WillPopCallback callback in _willPopCallbacks) {
-                callback.Invoke().then(v => result = !(bool)v);
-                if (result) {
-                    return  Future.value(RoutePopDisposition.doNotPop).to<RoutePopDisposition>();
+            Future InvokePopCallbacks(int index) {
+                if (index == _willPopCallbacks.Count) {
+                    return base.willPop();
+                var callback = _willPopCallbacks[index];
+                return callback.Invoke().then(v => {
+                    if (!(bool) v) {
+                        return Future.value(RoutePopDisposition.doNotPop);
+                    }
+
+                    return InvokePopCallbacks(index + 1);
+                });
-            return base.willPop();
-            
+
+            return InvokePopCallbacks(0).to<RoutePopDisposition>();
         }
 
         public void addScopedWillPopCallback(WillPopCallback callback) {