Flutter wait for listen() function

Question

I am trying to get a list of groups with this function: I am using GetX, RxDartand Streams.

Rx<Stream<List<FrediUserGroup>>> groupsStream = Rx<Stream<List<FrediUserGroup>>>(Stream.value([]));
  
List<FrediUserGroup> get groupList {
    List<FrediUserGroup> groups = [];
    groupsStream.value.listen((event) {
      groups = event;
      //print(groups) => [...,...,...,] prints list of complete groups
    });
    //always returns [];
    return groups;
  }

How can I wait for the listening to finish before returning the value?

OR How can I correctly return the listener function and return event inside of it (gives me an error: A value of type 'StreamSubscription<List<FrediUserGroup>>' can't be returned from the function 'groupList' because it has a return type of 'List<FrediUserGroup>'.