We've moved pieces of our game backend architecture from Python to Go, especially the bits that really benefit from high concurrency and possible parallelism. Moving the entire API is a monolithic task, but I imagine we'll eventually get there. But carving out the bits that need high speed, high concurrency (like sending 500 GCM notifications a second, for instance) really thrive.

Our client dev is all Unity, however, and I don't quite see Go entering our client dev cycle at all. And I'm a huge Go fan.