...and you can also have something like that using Bluebird.coroutine() (https://github.com/petkaantonov/bluebird/blob/master/API.md#...) or co (https://github.com/tj/co, see also https://github.com/koajs/koa)

Whaaa... they're putting experimental ES7 features in a transpiler called 6to5? Or am I missing something?

Definitely my preferred approach. Note that you need to run 6to5 with the -e flag to try this.

Where does it say that it supports async/await?