They're orthogonal? Coroutines as built here are just sugar around building the state machines you necessarily build by hand if you're using something like epol

They're orthogonal? Coroutines as built here are just sugar around building the state machines you necessarily build by hand if you're using something like epoll. They can also be used to model state machines in general, so long as there's a well defined progression of states in one direction. You would use these coroutines with tokio or mio, which are event driven frameworks that use epoll at their core on Linux.