Rephrased: ocaml is so flexible that async can be implemented as a library with no special support from the language.
This is the beauty of ocaml (and strongly typed functional languages more broadly)
I don't think that's anything specific to strongly typed functional languages. In eg Rust even the standard library relies on third party crates.
Though it is still somewhat amusing to me that loops in Haskell are delivered via a third party library, if you ever actually want them. See https://hackage.haskell.org/package/monad-loops-0.4.3/docs/C...
I do agree that it's good language design, if you can deliver what would be core functionality via a library.
Whether you want to integrate that library into the standard library or not is an independent question of culture and convenience.
(Eg Python does quite well with its batteries-included approach, but if they had better dependency management, using third party libraries wouldn't be so bad. It works well in eg Rust and Haskell.)
Clojure has core.async, which implements "goroutines" without any special support from the language. In fact, the `go` macro[1] is a compiler in disguise: transforming code into SSA form then constructing a state machine to deal with the "yield" points of async code. [2]
core.async runs on both Clojure and ClojureScript (i.e. both JVM and JavaScript). So in some sense, ClojureScript had something like Golang's concurrency well before ES6 was published.
[1] https://github.com/clojure/core.async/blob/master/src/main/c...
[2] https://github.com/clojure/core.async/blob/master/src/main/c...
That's wildly overselling it. Closure core async was completely incapable of doing the one extremely important innovation that made goroutines powerful: blocking.
(let [c (chan)]
;; creates channel that is parked forever
(go
(<! c)))
c := make(chan interface{})
// creates goroutine that is parked forever
go func() {
<-c
}()Call a function that blocks in go, the routine will park. Do that in Clojure and the whole thing stalls.
There is a caveat where Java code using `synchronized` will pin a carrier thread, but this has been addressed in recent versions of Java.[1]
Because JavaScript runs an event loop on a single thread. It's akin to using GOMAXPROCS=1 or -Dclojure.core.async.pool-size=1 . There may be semantic differences depending on the JavaScript engine, but in the case of web browsers, the only function that could possibly stall the event loop is window.alert. As for Node.js, one would have to intentionally use synchronous methods (e.g. readFileSync) instead of the default methods, which use non-blocking I/O.
When using core.async in ClojureScript, one could use the <p! macro to "await" a promise. So there is no use for Node.js synchronous methods when using core.async (or using standard JavaScript with async/await).
I would call this "making use of the platform" rather than "special support from the language". The core.async library does not patch or extend the base language, and the base language does not patch or extend the platform it runs on.