Good night can be said in many ways. Some examples include:
-Sleep tight
-Sweet dreams
Which one you choose depends on your relationship with the person and how you want to say it. If you want to say it in a more affectionate way, you could say "I love you, good night" or "Sleep well, my love." If you want to say it in a more casual way, you might say "See you in the morning" or "Have a good night."