Actually Java brought back the green threads model that it had before Go came to be.

The difference is that now red and green threads are exposed at the API level, and not an implementation detail.

Hardly copying Go.

Quoting "colored functions" is a problem of skill. It is a tell of engineer's lack of understanding of concurrency.

Can you please elaborate why?

> but that's nearly 20 years after Go was released.

Go 1.0 was released in 2012.

The concurrency model basically came from Erlang, which in my opinion does it better.

Colored functions is only a problem in JS

And C#, Python, Rust...

You can de-color an async function by blocking.

In most implementations, blocking in an async function has unintended side effect of blocking all other async function running on the same executor.

It's not the case in C#. It is discouraged, but mainly because there just used to be so much sloppily written async code that managed to bring down threadpool to its knees despite hillclimbing and blocked threads detection doing a lot of heavy lifting, so the community has grown scar tissue against this. It's rarely an issue if ever in the last 5 years or so.

And Python... And Rust... And C#...