Angelfish and Goldfish have different Temperature requirements. Angelfish are tropical fish which require warmer water. Goldfish are coldwater fish. Many hobbyists successfully have both species in the same aquarium.
Goldfish generate large amounts of waste. The water can get dirty quickly. Angelfish, being very sensitive about water quality, can be affected.
If the angelfish and the goldfish are to be kept together, ensure that the water is clean by performing frequent water changes.
Provide adequate space in the aquarium. Angelfish can get aggressive if they do not get adequate space.