My dad has a goat horn handle on his patch knife as well as a little priming horn made from goat horn in his shooting bag. However, these are from mountain goat, not domestic goats. The difference between "horn" and "antler" is that horns are all as bezoar describes, basically a sheath made up of the same material as finger nails (and hair) over a bone pedestal whereas antler is solid bone and is shed annually. With only one exception, horns are not shed. The one axception is the pronghorn (antelope), the only animal in the world that sheds horns. If you want to make a knife handle out of domestic goat horn, you could make a brass plate larger than the opening on the horn, drill a hole or file a slot to fit the shaft on the knife (that hold the handle) then slide the brass plate onto the knife, fill the horn with some kind of epoxy and put it on the knife being carefull to hold it tight against the brass plate and centered where you want it until it cures. Then just dress the brass plate down to the contour of the horn base and you have a handle.
Cody