For the sake of the goat's well being, please get
two goats. Why?
Goats are herd animals. Without a similar animal to herd with (another goat, sheep, alpaca, etc.) they will be miserable. Herd animals need that companionship, and humans
are not a replacement for it. If you try and keep a herd animal singly, then the animal will be incredibly
stressed out. Stress makes them more likely to fall ill.
Not to mention, if you try and keep a goat alone, you would need a pair of earplugs for yourself and anyone else in earshot. A lonely goat is LOUD. They herd call constantly. And it isn't a cute sound. It is a distressed screaming.
If you house the goats in your coop (I'd suggest building a new shelter, however. It doesn't have to be elaborate), you need to find out how to do several things. First, keeping goats out of chicken feed. Many a goat has gorged itself on chicken feed,
gotten bloat, and died.
How do you keep chickens and thus chicken poop out of the goat's food and water. I don't know about anyone else, but my chickens freaking LOVE getting into hay and mussing it up. Goats need hay,
clean hay. Goats also need
loose minerals to eat (mineral blocks do not provide enough trace minerals for them, if they rely on only a block, they will become deficient because they are getting mostly NaCl and not enough zinc, selenium, etc.), but they will not touch it if any poop has. Seriously, if a single goat raisin makes it into my mineral feeder, I have to change out the minerals completely before they'll touch it again.