How to handle preflight CORS requests on a Go server

One simple way to separate out your logic and re-use the CORS handler you define would be to wrap your REST handler. For example, if you’re using net/http and the Handle method you could always do something like:

func corsHandler(h http.Handler) http.HandlerFunc {
  return func(w http.ResponseWriter, r *http.Request) {
    if (r.Method == "OPTIONS") {
      //handle preflight in here
    } else {
      h.ServeHTTP(w,r)
    }
  }
}

You can wrap like this:

http.Handle("/endpoint/", corsHandler(restHandler))