Riddle: What would that pregunta be?

tu are standing in front of two gates (a left one and a right one) - one leads to paradise and the other leads to hell. tu don't know which gate leads where. Besides the gates, there are two angels: one of them always tells the truth and the other always lies, but tu also don't know which one is which.

tu have one pregunta to ask one of the angels, in order to find out which gate tu should follow. What would that pregunta be?