If the goldfish are small, they will probably get along with danios. However, larger goldfish can eat small danios, and danios sometimes will nip at goldfish. There are other reasons why I suggest keeping goldfish only with goldfish. I have a list at
http://www.fishpondinfo.com/gfish2.htm#otherFor your size tank, I suggest no more than three goldfish. They may seem small in the tank at first but goldfish can grow over a foot long eventually. Fancy goldfish usually stay under 8 or 9 inches long at maturity in aquariums.
Good luck!