Having only briefly looked through the code base of libgo. It looks like they use boost::context, which is the only good stackful coroutines implementations I've come across. Not being familiar with your project I'm slightly confused about the statement of "hundreds of thousands of short-lives micro-tasks". This is usually a no-go in case of stackful coroutines, as you would waste too much memory as well as have a lot of overhead.

Regarding your debugging issues. I'd be surprised if this doesn't improve over the next year or two. Clang afaik isn't even fully compatible with the final version of coroutines yet. Microsoft has done a lot of work on the compiler itself. I'd assume that Visual Studio will likely ship improvements once they release VS2022(?). Of course these are only guesses from my side.

Summing it up it sounds to me like you suffered from the curse of being an early adopter. It would be interesting to see if you'd have less issues once tooling and compiler support has improved enough.