Describe the bug
When attempting to set the bytes for the packet GAME_STATE_CHANGE it returns a FieldAccessException.

I've tried using:

PacketContainer packet = new PacketContainer(PacketType.Play.Server.GAME_STATE_CHANGE);
packet.getBytes().write(0, (byte) 4);
packet.getFloat().write(0, 1F);

To set the bytes for the GameState.

Screenshots

Version Info
ProtocolLib build 524
Dump: https://paste.helpch.at/epotetaqis.pl

Looks like Mojang made an internal pseudo-enum for this. The packet is encoded to/from a byte, which is why it's represented that way on wiki.vg. I'll look into a good way to read those

Actually you should be able to access it with packet.getGameStateIDs()

Actually you should be able to access it with packet.getGameStateIDs()

How exactly would it be done with that?

int stateId packet.getGameStateIDs().read(0);
packet.getGameStateIDs().write(0, stateId);