[throwaway34241]

I'm working on a UI app in Go, yes I think you'd use channels and message passing but it doesn't look all that bad in practice.

First you'd probably call runtime.LockOSThread() to tie a goroutine to an OS thread if the native API you're coding against needs that (like Cocoa, OpenGL, etc).

To perform work on the main thread using closures is probably the most convenient way. So you just have a RunOnMainThread(func(){...}) that puts the closure on a channel to run on the main thread (or uses some similar feature from the underlying native framework).

It's not terribly inconvenient - it's similar to the old Cocoa / UIKit performSelectorOnMainThread: method except that you have closures to make things simpler.

There's probably a little syntactic overhead compared to if you had several async/await functions running concurrently on the main thread. But on the other hand it's probably a bit easier to reason about, since the flow of execution on the main thread is very straightforward (if you have multiple async/await functions running at the same time on the main thread, it seems like every time they await a result they'd have to worry about other code being run on the main thread, and make sure they release any locks, etc).