got some input on that. gg in online games is mostly a (respectful) handshake in online games - this is not necessarily how it is meant by evryone, but for sure a way to interpret it. In contrast to gg ez which is a taunt.
In 2000 or so games there were three uses of gg by people before game end:
- no matter how it ends, it already was a good game (probably clearer when people write gg wp)
- I seem to have lost already at this point [often to complain about luck or to throw you off, by getting you overconfident]
- "It is clear, this is 100% over", on top of the normal gg meaning (people that are less good often enough misjudge that); my variant of this also states disappointment in the opponent that had a shot of winning but just threw it away with one move and made it a 100% win for me - OR just a statement of fact when the relevant cards were opened
mind you, my experience is only in realtime games.
--sP