Yes a gold fish can go in just a glass bowl without a filter, but considering they're not the cleanest of fish, they are better in a 2-5 gallon tank with a carbon filter and bio wheel.
If you keep your friend in a bowl you may have to clean it every other day, which gets kinda annoying and stressful to the fish.
If you can handle a fish in a glass bowl for a month, I would upgrade him. He'll be happy!