Setup. Keeper in goal. Shooter 12 metres out in the middle. A second player lurking 8 metres out to one side.
How it runs. The shooter strikes low to one side. If the keeper holds it, the rep is over. If it is parried or dropped, the ball is live and the second player shoots it first time, wherever it lands. The keeper gets up, gets set and saves again. No stopping, no apologising, no looking at the coach.
Make it harder. Two lurkers, one each side. Then the first shot is hit hard on purpose so there is always a rebound.
With 4 keepers. Keeper, shooter, lurker, one resting.