Setup. Keeper in goal, facing the net with their back to the pitch. Two servers 10 metres out, a ball each.
How it runs. The coach points at one server, then shouts "turn". The keeper spins, finds which server has stepped forward, sets and saves the shot. The shot comes one second after the shout. Six reps, then rotate.
Make it harder. Three servers. Then the keeper starts lying face down. Then the keeper starts by catching a ball thrown from behind the goal before turning.
With 4 keepers. Keeper, two servers, one resting who does the pointing.