Close send channel in test (dart-lang/stream_channel#54)

Without closing this channel the VM will not exit. Refactor to
`async/await` so that we can close the channel only after receiving the
expected items. This allows running the test directly in the VM without
the test runner.
1 file changed
tree: ba9ac5878a6ad4f24719fc4fddaac61fcc3ad354
  1. pkgs/