you are in a pitch black void. Before you are two white, identical doors. The doors began to speak.

The doors:"we are your only chance of escape from this void."

Left door:"one tells the truth..."

Right door:"... And the other always lies."

Left door:"pick the correct door, and you're free..."

Right door:"pick the wrong door, you are stuck here forever."

The doors:"you may, however ask us anything, to tell us apart. So, what shall you ask?"

What do you ask the doors?