如何实现线程为我的游戏添加计时器？

I've written the MVP for a game. But now I would like to add a stopwatch to it, so that the player can see time being counted down in the bottom left or right corner of the game. This isn't a question about how to create such a stop watch, its about how to include it in my game.I've written the MVP for a game. But now I woul