Like a walk-in closet, a walk-in pantry is basically a small room in your home. Install at least one ceiling fixture in your walk-in pantry, or more if the pantry is quite large. Simple fixtures such as plain-glass globes or fluorescent tube fixtures work well because they're hidden behind the pantry door, making the fixture's style unimportant. If, on the other hand, your pantry has a glass door or an otherwise-visible interior, or if your home is upscale, consider hanging something more substantial and decorative.
A built-in pantry is more like a kitchen cabinet than a walk-in closet. Built-in pantries are typically smaller than walk-in pantries, so a small, flat light fixture is probably your best choice. A small, flush-mount fixture is a good choice, as is a fixture with a very low profile, perhaps 1 or 2 inches deep. If there's no room to install a light fixture, consider hanging an adjustable spotlight on the ceiling in front of your pantry, and angle the light so it illuminates your shelves when the pantry door is open.
If you have a free-standing pantry, which is a piece of furniture rather than a built-in cabinet or a small room, chances are it doesn't have lighting. If it's dark enough inside that you have trouble finding what you need, a few well-placed wireless lights are a smart solution. Wireless lights are battery-operated and often install with adhesive, so they don't need to be wired in and you can stick them anywhere. Look for LED models, because these have a long battery and bulb life.
No matter what type of fixture you end up selecting for your pantry, have your electrician install an automatic on and off button, if possible. This low-tech addition works like a refrigerator light, your pantry light coming on when you open the door and going off when you shut it. As many times a day as most pantry doors are opened and closed, this one simple addition makes a big impact.