Most goats are fairly self-sufficient so your shelter can be pretty rudimentary. Goats need to be able to stay dry, they DO NOT like being wet and they hate walking in mud. So obviously the shelter you provide needs to protect them from the rain. Orient the opening of the shelter opposite from the prevailing winds. If you live in a warm or hot climate, like Texas, your shelter needs to have good ventilation. Texas goats tend to lounge and sleep out in the open during good weather, even cold weather.
We like to provide, what we call a bench, in each shelter. The bench simply allows the goats to get up off the ground should they choose to do so. We have some benches built out of dimensional 2X lumber and others are as simple as a pallet topped by plywood.
If you build your shelter with metal or plywood siding, it would be a good idea to install "bump boards" around the inside to protect the walls. If you have been around goats for more than five minutes you know that they tend to butt one another and oftentimes literally slam into other goats. The bump boards are normally made using 2X6 inch lumber set at about shoulder height to your goats all the way around the interior walls. The bump boards will prevent your goats from pushing out your walls.
Here, in our part of Texas, it is not necessary to cover the ground inside the shelter with bedding material such as, wood chips or straw. In colder climates, that may be true because it will provide insulation between the goat and the cold ground. What we have found is that our goats always seem to scrape away the bedding material and lie directly on the ground.