Quite often I see goalkeepers warming up with the rest of the team before a practice or a game. Or they go straight into goal and take shots from a coach. The latter is the worst thing to do. Keepers have very different body motions during a game as compared to out players. Therefore they need a different routine to warm-up, stretch and get ready. In addition, more than out players, keepers live from confidence. So their warm-up isn’t only physical but also mental. Lastly, keepers have less running and action during a game and usually don’t get many opportunities to touch the ball (more so with feet these days) with their hands. So a good keeper warm -up also functions as additional practice and skill development.
Here is a session I have developed for youth goalkeepers understanding that a routine for adults or professionals might be a bit different and typically has more time available.