Websocket fix (#623)

* Fix panic when Tr is nil

* Explicitly call handshake for tls connection

https.go

@@ -76,7 +76,7 @@ func (proxy *ProxyHttpServer) dial(ctx *ProxyCtx, network, addr string) (c net.C
 		return ctx.Dialer(ctx.Req.Context(), network, addr)
 	}
 
-	if proxy.Tr.DialContext != nil {
+	if proxy.Tr != nil && proxy.Tr.DialContext != nil {
 		return proxy.Tr.DialContext(ctx.Req.Context(), network, addr)
 	}
 
@@ -651,5 +651,9 @@ func (proxy *ProxyHttpServer) initializeTLSconnection(
 	if ctx.InitializeTLS != nil {
 		return ctx.InitializeTLS(targetConn, tlsConfig)
 	}
-	return tls.Client(targetConn, tlsConfig), nil
+	tlsConn := tls.Client(targetConn, tlsConfig)
+	if err := tlsConn.Handshake(); err != nil {
+		return nil, err
+	}
+	return tlsConn, nil
 }