Comment by _flux

> Go channels aren't unique, because by the time Go came around pretty much every primitive had been tried somewhere, but it is to my knowledge the only langauge that lifted channels up into the language itself and made them first class.

Concurrent ML had something like that, and it was implemented in OCaml as well: https://ocaml.org/manual/5.5/api/Event.html

And I would say it even goes further than Go by making the actual events first class (no need for language support for this either): send, write and choose (aka select) are also events, so you can build your own things you can select on. Select would be basically defined as

    let select events = sync (choose events)

so sync is the way to convert events to values (and blocking in the progress).

CML had one extra trick in its sleeve: it was able to garbage collect threads that were not able to proceed. I'm not aware of any other system that can do that. This would e.g. resolve leaking coroutines in Go, at least in some situations..