Here are your parts.
Parts for Whirlpool ET22DKXFN00 Refrigerator - AppliancePartsPros.com

Check to be sure that the compressor is running.
You can usually hear it but you should also be able to feel it vibrating and it should be warm.

Check that the condenser/compressor fan is running and that the condenser coils are clean.

Check that the evaporator/freezer fan is running.

If all OK remove the cover in the freezer so that you can inspect the evaporator coils.

If they are heavily frosted/iced over you have a defrost problem.
Should be repairable at a fairly reasonable cost.

If there is no frost or just frost in one area (usually where the freon enters the coils) you have a sealed system problem. Be sure to check it after the compressor has run for a couple hours. If you check it shortly after a defrost cycle you will come up with the wrong conclusion.
This will be an expensive repair as you need a pro. Often it makes more sense to put the dollars towards a new unit.

Here is a good link check out the example pictures, about half way down the page.
http://www.applianceaid.com/refrigerator-not-cold-enough.php

Check the unit's warranty often the sealed system has a longer warranty.