Actually, goldfish will eat lots of "people food" ... good choices are:
1. Chopped up (cooked) salad shrimp. <They love shrimps!.>
2. Peas - blanched, shelled & chopped. <Great for constipation.>
3. Cucumbers & zucchini - sliced & blanched, cut rounds in half so they can get into the middle.
4. Other leafy veggies - generally you need to blanch it to soften & feed on a veggie clip ... this is hit & miss, some fish like certain veggies, some won't touch it.
5. Tiny bits of chopped sardines or other fish.
6. Small amount of fruits - oranges, pears, apples.
If you are really ambitious, you can cook for your goldfish. There are recipes of gel food for goldfish, involving chopped sardines, pureed veggies, added vits & gelatins.
Otherwise, sinking pellets supplemented with whole foods is a good diet for your fish.