You probably already know the phrase "Good luck!", which people say to cheer someone on. You may also know "Good luck with (something)":
Yeah, good luck with that.
But people also say "Good luck in ___" or "Good luck at ___" when a person is leaving to move to a new place:
Good luck in Delaware!
Good luck at your new job.
You choose whether to use "in" or "at" based on what words follow it:
- "in" Boston, France, Australia
- "at" school, your new job