Final answer:
A goalkeeper in ice hockey can be replaced by a skater and is allowed to re-enter the game at any time, either during a stoppage in play with puck possession by their team or in a none-risk situation.
Step-by-step explanation:
According to the rules of ice hockey, a goalkeeper may be replaced by a skater during play, often in scenarios like a delayed penalty or for an extra attacker towards the end of the game. Once the goalkeeper is off the ice, they are permitted to re-enter the game at any time. The goalkeeper can rejoin play either during a stoppage in play when their team has possession of the puck or if there is a guaranteed none-risk situation, meaning, for instance, the puck is at the other end of the rink. It's important for the team executing this maneuver to be strategic and vigilant to avoid leaving the net unprotected unnecessarily.