Depends who you ask and No. Aquarium salt when used appropriately for short periods of time is not harmful, but it's completely unnecessary can ultimately cause kidney failure is often dosed in excess, and is difficult to actually remove.
Basically don't... There's no good reason for it especially of you want your fish to have energy. Make them happy with clean water and an appropriate environment and they will be more active for you.
If you want your goldfish to be more active then feed them better quality food and increase the flow on the tank if they are of the single tail variety. The fancies tend to be more relaxed while the single tails tend to be swimming around more especially when food is involved.