Global scaffoldMessengerKey to show SnackBar, but Flushbar?

[danielrrys]

FlutterError: Navigator operation requested with a context that does not include a Navigator. The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.

I decided to change to Flushbar, before I used the Snackbar default, but before it occupied the GlobalKey<ScaffoldMessengerState> in the main.dart MaterialApp to show the Snackbar as :

messengerKey.currentState!
      ..hideCurrentSnackBar()
      ..showSnackBar(snackBar); 

And have a better control in all my application of the Snackbar, but in Flushbar I don't know if I can really use it like that.

If I use flush.show(messengerKey.currentContext!); i have that error