releaseSink<
    Releases results added to the returned sink as data and errors on sink.
A Result added to the returned sink is added as a data or error event
on sink. Errors added to the returned sink are forwarded directly to
sink and so is the EventSink.close calls.
Implementation
static EventSink<Result<T>> releaseSink<T>(EventSink<T> sink) =>
    new ReleaseSink<T>(sink);