I agree it's always left a bag taste in my mouth. I loved generators and yield/yield from, but I was stuck on 2.7 for a long time so I never quite understood the motivation for async/await over them.

One issue is that it "reifys" the "colored function" problem that green threads like goroutines don't have!

Side note: Java world is working on green threads/fibers for the JVM in Project Loom.

[0]: http://cr.openjdk.java.net/~rpressler/loom/Loom-Proposal.htm...