Generics in go, as they're implemented today, sadly have a fair bit of performance overhead. I haven't tried but my assumption would be that go generics are not fast enough to make an effective arena allocator. I'd be thrilled if someone could prove me wrong though!
The performance overhead is when you're calling a method on the generic type--Go has to lookup the specific implementation in a dictionary. Pretty sure that doesn't apply for straight-up container use cases like this one.
