Yes, there are systems to tap into a live gas line (Or high pressure steam or water lines, etc.) BUT if your not familia with the procedure DON’T even try it.
I did it a few times on city cast Iron gas mains 36″ diameter but would never even try to explain how on here.
I would strongly suggest you check out contractors that do this all the time and who carry heavy insurance.
One mistake and you bought the farm.
SylvanLMP