I enabled a new hunger feature. The game will shrink the world border by one block per minute, to a minimum radius of 20 blocks. This is to prevent a game where 6 people start, a huge map is created and the leftover two get stuck in opposite corners for hours without doing anything to bring the game forward.
The setting of a smaller world border is triggered by people joining, leaving or switching worlds. So if there is no activity on the server beyond the theoretical maximum duration of the game, the world will keep the same size. If there is a lot of activity, it will shrink every minute by one block, if there is less activity, it will shrink in larger jumps. This is to prevent to have too many triggers when the server is busy that might overload the server.
If you are cornered by a shrinkage underground, you should be teleported to the surface. So be aware about the time of the game, and do not corner yourself! It should not kill you however.
This is still up for testing. Please try it out so we can adjust it when necessary.