Somebody should write a Google Go to C transpiler. Mostly Google Go features are limitations or different styles in order to 'improve' C, so it should produce fairly readable C code. Then you could use any compiler, linking type, combine with any language, etc. You could probably even use LD_PRELOAD to replace coroutines with pthreads.

For instance Russ Cox did coroutines and channels in his C libtask in a few thousand lines of code. It's not pretty but it works. Include something like it behind an API as 'libgrt.o' with a few other features and the rest of the code transpiles cleanly.

...but say this existed. What would be the point of writing Google Go code? A more compiler-friendly syntax, less flexibility to make simple memory/pointer mistakes? Would that be enough or would you, with perfect C linkage, just end up writing most of the code in C and Lua? It certainly seem the effect of creating their own compiler (worse than gcc), an opaque "go" tool that does everything, project layout and hosting rules, complicated FFI, etc is to make a 'toolchain island' locking you into writing everything in Google Go, where you might not otherwise.