Switch is in the latch.
You can verify this when you have a bulb that is ok.
With the trunk open, the light on, slide the latch of the body, not the trunk latch. The light goes off. Of course, return the body latch before you slam the trunk.

WARNING TO ALL ROADSTER OWNERS - make sure you fully latch the trunk closed. If not the light will stay on. Happened to me once, and I hadn't used the car for several days. Battery became completely dead.
Took me quite some time to figure out why the battery was dead.