Handle pre-flight requests (#20)

* Revert "Add cors headers to every response (#19)"

This reverts commit 87b0601.

* Handle pre-flight requests

pkg/torproxy/torproxy.go

@@ -261,7 +261,12 @@ func reverseProxy(redirects []*url.URL, lis net.Listener, dialer proxy.Dialer) e
 		http.HandleFunc(removeForUpstream+"/", func(w http.ResponseWriter, r *http.Request) {
 
 			// add cors headers
-			addCorsHeader(w)
+			addCorsHeader(w, r)
+
+			// Handler pre-flight requests
+			if r.Method == http.MethodOptions {
+				return
+			}
 
 			// prepare request removing useless headers
 			if err := prepareRequest(r); err != nil {
@@ -286,7 +291,10 @@ func withoutOnion(host string) string {
 	return strings.ReplaceAll(hostWithoutPort, ".onion", "")
 }
 
-func addCorsHeader(w http.ResponseWriter) {
+func addCorsHeader(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodOptions {
+		return
+	}
 	w.Header().Set("Access-Control-Allow-Origin", "*")
 	w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
 	w.Header().Set("Access-Control-Allow-Headers", "*")