I think the hard part here is not language design, it’s implementation of the runtime. Linux is especially problematic, asynchronous IO has arrived late, years

I think the hard part here is not language design, it’s implementation of the runtime. Linux is especially problematic, asynchronous IO has arrived late, years later than IOCP and kqueue. It took multiple kernel versions to make it usable, and still the APIs are questionable, e.g. files and sockets use different ones. Even MS failed to do it right, see a bug I found: https://github.com/dotnet/corefx/issues/25066 https://github.com/dotnet/corefx/issues/25066