When the attackers are training an attack system, the goalkeeper might get bored, but that can be remedied.

In the shown example the attacking team practice the French Cross:
As soon as the backcourt player throws the ball to PM, the goalkeeper activity starts.
The goalkeeper must move from the center of the goal to the different cones and touch them.
This must be done so fast, that the goalkeeper is back in the goal, when the French Cross is made and the shot is taken.
The distance to the cones are adjusted in accordance with the goalkeeper/attacking players speed. If the pressure is on the goalkeeper a longer distance between the cones are made. If the pressure is on the attackers, a shorter distance is made.