Well sure --gc:boehm and --gc:go are shared memory GCs and they work with async as far as I can tell. As I said "araqsgc" is a hybrid, it will work with async too.
And yeah, I'm very willing to make `ref` and `closure` atomically refcounted **if that 's what it takes**. However, to me it's an open question of whether `async` intrinsically really needs it or the current async implementations need it or neither and I simply need to add some problem-specific "tracking" like task IDs in order to make it work.
