The Billikens (6-6) trailed for most of the first half and went into the intermission down 38-30. They opened the second half with an 18-3 run and never trailed again.
The Camels (5-6) used an 8-1 run to close within 60-56 on Chris Clemons' free throws with 3:34 left, but Goodwin stopped the momentum with a 3-point play and Saint Louis made 9 of 12 free throws to go with Davell Roby's layup to hold on to the lead.
Johnson made all three of his 3-point attempts, all six of his free throws and 4 of 6 overall from the field for Saint Louis. Hasahn French added 11 points and 12 rebounds.
Chris Clemons had 28 points and Marcus Burk had 20, accounting for all but 18 of the Camels' points.
Michigan blows out Nova in rematch of 2018 title game
In a rematch of the 2018 National Championship Game, Michigan dominates Villanova in a 73-46 victory behind 19 points from Charles Matthews.
Williamson, No. 1 Duke rout Eastern Michigan 84-46
Zion Williamson scored 21 points, fellow freshman RJ Barrett added 20 and No. 1 Duke routed Eastern Michigan 84-46 on Wednesday night in its first game this season as the nation's top-ranked team.
Michigan routs Villanova in championship rematch
Charles Matthews scored 19 points, Ignas Brazdeikis had 18 and No. 18 Michigan beat No. 8 Villanova 73-46 in a national championship game rematch Wednesday night.