But after writing tons of Go over the past 2-3 years, going back to async code, even with the tornado sugar, just feels like driving a manual car after getting used to automatic. It's just redundant. I've seen better, I've written way cleaner code and got better concurrency. Promises, futures, yielded generators - they are all syntactic hacks. The only language I've used that really addresses this properly is Go (disclaimer: I haven't written any Erlang).
I think Clojure (core.async), Haskell (GHC), and Rust would also give you what you're looking for.