Solve the riddle! i still can't figure it out :(?

there was a peasant who had no choice but to steal from the king in order for his family to survive. but he got caught, and he was brought infront of the king. the peasant previously has impressed the king so his highness decides to give him a second chance. so he locks the peasant in a cage with 2 doors. one door to freedom, one door to death. the king places two guards near each door. the peasant is allowed to ask one question, and one question only from one of the peasants. one of the guards will tell the truth, the other will lie. the peasant asks one of them a question, and the reply to this question will help him free himself! what was the question?