I agree with everything that has been said. Seems that you haven't even started to cycle your tank. You must give the tank time to establish good bacteria - that bacteria is going to be able to successfully break down the waste that is produced by your fish and it's food. Without it, you have high ammonia and nitrites that almost always mean instant death for your fish. In addition it is also possible you are not choosing hardy enough fish.
If I may ask what you are trying to add?
Hardy fish will most likely not die through a cycle (though they can have damaged gills and not live as long as they would with a fishless cycled tank), and a lot of people will use fish to cycle a tank. White Cloud Minnows, Zebra Danios, Cherry barbs, etc, tend to be the hardiest. There are also some very hardy tetras that seem to do good, but you must know your tetras. Neon tetras are notoriously bad at being hardy, only becoming "used to" abuse after several years of being alive. They don't do very well in hard water systems, and almost always need a tank that has been established for a while. Gouramis also tend to be on the sensitive side, and aren't a good choice when trying to cycle a tank, though most likely hardier than neon tetras.
*edit* Oh, I just saw that you tried to add goldfish? Goldfish are hardy, BUT not when you add in large ones into a tank that isn't cycled. Goldfish produce the ammonia you need, but they often overload the system with it, which is BAD NEWS for any fish in that tank - no good bacteria established to break down all that ammonia. Not to mention, what does "2 large goldfish" mean? Are they over 6" big? 12"?; if they are fancies, I'm pretty sure they'll need at least a 40 gallon. If they're adult common/comets I'm pretty sure 2 need at least a 55 gallon. I'm not an expert on goldfish, just have read a lot. They need A LOT of room. My advice would be to not get anymore goldfish because your tank can't handle it.
*edit*
The temperature of the tank will also determine if maybe it's too warm or too hot for what you're adding. Also, how do you acclimate your fish? The way you acclimate your fish may also tell us why they are dying so fast.
