Cast use of StreamSubscription.cancel result through dynamic (#105)

diff --git a/test/subscription_stream_test.dart b/test/subscription_stream_test.dart
index 0b24a02..98a809f 100644
--- a/test/subscription_stream_test.dart
+++ b/test/subscription_stream_test.dart
@@ -65,7 +65,7 @@
     subscription.resume();
     expect(controller.isPaused, isFalse);
 
-    expect(await subscription.cancel(), 42);
+    expect(await subscription.cancel() as dynamic, 42);
     expect(controller.hasListener, isFalse);
   });