I am sorry to hear about your ignition issue. You stated that you have been to your local shop and they were unable to fix the problem. Were they able to duplicate the problem? Is this a new problem? If not, how long has it occurred? Is it possible the key is in the wrong ignition position, or is between the 'Lock' and 'Off' positions, eventually falling into the 'Off' position allowing you to remove the key? Referring to pages 2-15 and 2-16 of your owners manual.
If that is not the issue, please pm me your name and VIN number and I will research the issue further. I look forward to hearing from you.
Louis
GM Customer Service