You can’t trade for a good goaltender during the season.
It’s become conventional wisdom in the NHL’s cap era, and it’s not hard to see why. If your team finds itself needing a goaltender, you’re almost by definition dealing from a position of weakness, so prices will be high. And the market is never all that exciting, for the simple reason that contending teams aren’t trading their goalies, and bad teams are usually bad because their goaltending stinks to begin with. So if find yourself needing an upgrade in net, you’re better off waiting for the offseason.