The Firbolg's Hidden Step trait (Volo's Guide to Monsters, p. 107) reads:
As a bonus action, you can magically turn invisible until the start of your next turn or until you attack, make a damage roll, or force someone to make a saving throw. Once you use this trait, you can't use it again until you finish a short or long rest.
I’m thinking about running a Firbolg Cleric, but I’m not sure if the Firbolg’s natural bonus-action invisibility from the Hidden Step trait can be maintained if I cast a spell.