A simple C coroutine library, with multithreading and more, Go and C++20 style

Like you mention other libraries, but how does this compare to something like this?

https://github.com/Keith-Cancel/Bunki

when compared to context switches having just giving things a cursory glance.

Also it seems to be trying to handle a lot of styles/handling of co-routines. Is there a reason for not really just choosing one style

Wow, C89 and it works on Windows. This is very neat.