I'm not sure exactly where you see that so I'm not entirely sure of the context (I tried looking in the first chapter), but a general problem with garbage-collected languages is that while the runtime will eventually get around to cleaning up unused resources, you don't always have guarantees about when. So you still generally need to close files when you're done with them, or you may run out of filehandles. I've encountered this issue in multiple languages, it's not Go-specific.