2018 ats with dead battery and doors locked. how do i open trunk or door

There may be a key hole in the deck lid near the push button. There is a key in your fob.

If you can get to the starter put a jump wire on the + cable and ground another , then you need a spare battery to hook them to and that may power it up to get in

Carefully look at your key fob. Most GMs have an emergency key hidden on the fob that flips out. Then look at the driver's door handle for a small cover that can be removed to insert the key. Jim