Mooby the Golden Sock
Yes, ECT (electroconvulsive therapy) is still used today. Yes, it is normally done voluntarily. Yes, memory loss is a potential side effect, though it is less common with the newer techniques.
No, getting ECT is not a reliable way of getting rid of a painful memory you want to forget. No, you can't just walk in and ask for it: it has to be ordered by a doctor.
I would like to add something else, the memories that get erased by ECT are completely random and the erasure is sometimes not total, you could just as easily forget some extremely pleasant memory as the unpleasant one you wish to be rid of. You would be far better off consulting a psychologist or a psychiatrist and learning how to confront that memory and deal with it in a healthy way.