Any language which is dataflow based will be great in an async context. Async is hard in most languages because they are imperative, which stands in stark contrast to the whole idea of asynchrony. This whole exercise of adding async features to various imperative languages is coming at the problem from the wrong way around in my opinion. It's a recognition that async programming is hard in imperative languages, and the thought is that maybe this could be made better with more language features. But the sad truth is that async features clash hard with the imperative nature of most mainstream languages.