Shaka describes his life on the streets as "rolling the dice and gambling with my future." (17.31) But when he's facing a murder charge he can't beat, he says
The game was over, and I had no future left to gamble. (17.32)
Gambling is a standard image for risky behavior, and Shaka really sells it here by the way he phrases it. Basically, he's saying he's out of time to play the game, and he's out of something to gamble on.
Only instead of money, he's been gambling with his future. So running out is a complete disaster.
It's a set of imagery that really brings home what a tough situation he's in.