fetchNextList.dart

List<DocumentSnapshot> documentList;  

fetchNextMovies() async {
    try {
      updateIndicator(true);
      List<DocumentSnapshot> newDocumentList = (await Firestore.instance
              .collection("movies")
              .orderBy("rank")
              .startAfterDocument(documentList[documentList.length - 1])
              .limit(10)
              .getDocuments())
          .documents;
      documentList.addAll(newDocumentList);
      movieController.sink.add(documentList);
    } on SocketException {
      movieController.sink.addError(SocketException("No Internet Connection"));
    } catch (e) {
      print(e.toString());
      movieController.sink.addError(e);
    }
  }