Source: Player's Handbook

When you use your action to Dash, you can use a bonus action to make one melee weapon attack or to shove a creature. If you move at least 10 feet in a straight line immediately before taking this bonus action, you either gain a +5 bonus to the attack’s damage roll (if you chose to make a melee attack and hit) or push the target up to 10 feet away from you (if you chose to shove and you succeed).