[Blackthorn]

What? No. You could not be more wrong. core.async does not support the first point in the least.

Don't believe me? Make a go block in core.async and have it call another function, then have that function block. Do it 10,000 times. I'll wait. And wait. And wait. And wait...get the picture?

Clojure has this in Pulsar, which is a library...that happens to perform bytecode modification to support this (which I consider to be on the same level as special support from the underlying level). Pulsar is an absolutely amazing project and I'm not trying to take anything away from it with this comment, but merely trying to illustrate how far off you are.