Yeah, the ML parts aren't in Go. I'm working in TensorFlow, so it's C++ scripted by Python. But there's a lot of incidental stuff that needs to be done, most of which I don't want to spend cycles on thinking hard about, and Go does a good job there, in that narrow niche where I want something that runs on one machine but find python too slow.
At a previous gig, I had done a lot of F#, and I think that's close to my personal sweet spot, but I'd have to use it frequently to keep it in my head. Go is small enough that I can load it into cache when I need it.