Earlier quoted context omitted.
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 lo…
it does not look like it's using boost::context. At least I never saw it in runtime. It's using its own asm routines for save/restore the context.
As far as I can tell the developer is using Fibers on Windows and boost::context on all other operating systems. You can see that he has a forward declaration in "libgo/context/fcontext.h" and then links against the respective boost assembly files in the CMakeLists.txt.