1. Go's spec and standard practices are more stable, in my experience. This means the training data is tighter and more likely to work.
2. Go's types give the llm more information on how to use something, versus the python model.
3. Python has been an entry-level accessible language for a long time. This means a lot of the code in the training set is by amateurs. Go, ime, is never someone's first language. So you effectively only get code from someone who has already has other programming experience.
4. Go doesn't do much 'weird' stuff. It's not hard to wrap your head around.