The universe is a little bit bigger that earth, especially outside our observable light cone. If there is alien intelligence out there, it is reasonable to assume that a game mathematically equivalent to go has been invented elsewhere. (Because I feel like if there are any other alien intelligences out there, there would be a very, very large number of them. The anthropic principle might explain a single intelligent species, but just 2 or even 1 million seems very unlikely given the quantities involved)