The deal will begin in the 2020-21 season.
McGing, 21, was the Blues' fifth-round pick (No. 138 overall) in the 2018 NHL Draft. He has spent the last four seasons with Western Michigan University, where he has posted 46 goals and 71 assists (117 points) in 147 collegiate regular-season games.
In 2019-20, McGing scored 13 goals and 22 assists (35 points).