Goalkeeping drills: The 4 goalies war!!

This one is a fun drill for goalkeepers by Flux Keepers: 
1. It involves 4 goalies, each one of them have to defend one goal.
2. The goalies are divided in two teams of 2 each.
3. They start facing outside.
4. At the signal, the coach sends one ball in and the goalies have to react!