Makefile,internal: fix websocket regression and other small things (#830)

- fix websocket regression and add test to prevent in the future
- fix staticheck errors
- remove proxy package remnants from Makefile 

fix #829

internal/router/peer.go

@@ -62,13 +62,12 @@ func NewPeer(cfg config.Config, logger *logmon.Monitor) (*Peer, error) {
 			IdleConnTimeout:       time.Duration(peer.Timeouts.IdleConn) * time.Second,
 		}
 
-		reverseProxy := httputil.NewSingleHostReverseProxy(peer.ProxyURL)
-		reverseProxy.Transport = peerTransport
-
-		originalDirector := reverseProxy.Director
-		reverseProxy.Director = func(req *http.Request) {
-			originalDirector(req)
-			req.Host = req.URL.Host
+		reverseProxy := &httputil.ReverseProxy{
+			Transport: peerTransport,
+			Rewrite: func(r *httputil.ProxyRequest) {
+				r.SetURL(peer.ProxyURL)
+				r.Out.Host = r.Out.URL.Host
+			},
 		}
 
 		reverseProxy.ModifyResponse = func(resp *http.Response) error {