Adding a light in the garage
If you only have hot and neutral in a light fixture a ground wire in a plastic fixture is not required in the latest version of the national electric code 2017 and the preview version I have will not have a change for non conductive luminaries , lighting fixtures for the general public but more than light fixtures is covered. Plastic or non conducive fixture no grounding conductor is required ( the green or bare copper wire is not required even today.!