To paraphrase a semi-relevant movie, "you're gonna need a bigger tank (and filter!)"
Average size of an adult "feeder" (common/comet) goldfish is 12-14 inches (and they can get bigger!). Probably too big to even physically fit in a 2 gallon tank! And they are active fish! As stated above, they're best kept in ponds. A tank for them that is the appropriate size would be more on the order of 200 gallons than 2 gallons. Shrimp, snails and betta fish are good options for a 2 gallon tank. If you want to rescue a goldfish, fancy goldfish tend not to end up much better off than their feeder bretheren, and stay somewhat smaller and can be kept in tanks as small as 20 gallons
Hope this helps!