How do I make my dome light fade away when you shut the door?

Thanks for the input guys.

I'm not savvy enough to build one from scratch, but I appreciate the link slantsixdan.

The diagram that Cheddar Greg provided looks like there is a purchased timer module used. I looked on the related site, but didn't see it as being offered.

I wonder if the the delay is built into the newer lamps or if it's in the wire harness itself.