You will not be able to open the door with a coat hanger between the window and door. The lock rod is protected to prevent this.
To reach the door unlock button you will need a 1/4" rod bent at a sharp 90 deg about 1 " and the rod will need to be 4-5 long , bent slightly in the middle as needed to reach the lock button through the rear upper corner of the door. Have someone guide you from the other side of vehicle.
The best option is to call the dealer and give them your VIN number off the dash. and with proper proof of ownership they can cut you a new door key with the factory code.
Any GM dealer can provide this for you. Should not cost much to get this done.