For large projects, it'd probably make more sense to rewrite the critical code sections in C. rubyinline makes this really easy, and ruby C extensions aren't that bad either.

One time on a contracting gig I had some code that was interacting with cairo drawing and imagemagick. They didn't have a compatible raw image format at the time (one was RGBA and the other was ABGR, IIRC.) It's trivial to convert between the two in ruby, but it was taking 60 seconds per image. Once I switched that one loop to C, it took 0.02 seconds.

I've got nothing against Go, just suggesting an alternative that might make more sense in some situations.