Brake stop light stays on had it in da shop but did not fix da problem

{: ) Did somebody worked on the BCM or your brake pedal? The wirings and connectors could have been knocked off. For the moment. let's just rule out the wiring issue first.
Under normal operations, the stop lamps get its power from the BCM (body control module). The BCM monitors the signals coming from the brake pedal sensor whenever you step on the brakes or not.
The component fix is to replace the brake pedal position sensor. I just hope your problem doesn't come to the point of replacing the BCM too (rarely happens).
But before proceeding with the replacement options, try to bring it to a shop with a GM scan tool and ask them to perform the brake pedal position sensor calibration. This is the quick fix without replacing any component. I hope you get lucky.