Almost every goalie I know has been there, tired of just popping into every single conditioning drill field players do. Not because it's hard, we can handle hard, but because it's not best preparing us for what we need to do in games.
In college, I started doing what I call Game Time Sprints which help accomplish a variety of things. You start in the middle of the crease in ready position, you can start at the cone on your right or left and work your way around the 8m back to the other cone. It is important to throw your stick out at each point, and when sprinting back always look into the middle in case a shot is thrown (just like a game!). See the image and video below for guidance! Happy running!
Enjoy my hard breathing!!! :)