I am new to D&D, and am playing 5th Edition. I have a level 3 wizard who has the spell expeditious retreat:
This spell allows you to move at an incredible pace. When you cast this spell, and then as a bonus action on each of your turns until the spell ends, you can take the Dash action.
The scenario is: On my character's turn, I want to Disengage from an enemy within 5 feet of me so as to not provoke an opportunity attack. I move my character 30 feet away. I then cast the spell expeditious retreat (which has a casting time of 1 bonus action) and then move another 60 feet.
The problem is that my DM says that I cannot take the Dash action, because he says that my bonus action is the casting of the spell. I believe that I can take the Dash action, because the spell says when you cast this spell you can take the Dash action.
Which one of us is correct?