Lots of neat and profitable games have been made in slower languages, so you should be fine, though in some cases you might have to replicate an entire engine... Not being real familiar with Go, the thing you'll want to look out for if your game gets "big" is unpredictable GC events, more-so even than the absolute max duration of any particular GC event. If Go (or whatever else) doesn't provide enough tuning to support "soft" realtime systems, you'll end up structuring your program to allocate in pools and release all references only at certain points to try and make the GC predictable, which is a common pattern for non-GC languages in games, so you've all but lost the let-me-not-care-about-memory-management justification for the language except for the safety aspects, which don't tend to be high priority for games...