In fact I don't, which was why I said "critical path in C, rest in Go". Usually I do Java but if I need to use C, I'd like to just write the part that needs to be fast, then drive it using something else. Python is also acceptable when it comes to parsing command line options and the like, and it's as slow as dogshit.

"Lots of free time" would be dicking around with cryptic STL error messages.