Merge pull request #3 from databus23/patch-1

Avoid passing empty headers during upgrade

Author: fatih

websocketproxy.go

@@ -136,10 +136,12 @@ func (w *WebsocketProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 
 	// Only pass those headers to the upgrader.
 	upgradeHeader := http.Header{}
-	upgradeHeader.Set("Sec-WebSocket-Protocol",
-		resp.Header.Get(http.CanonicalHeaderKey("Sec-WebSocket-Protocol")))
-	upgradeHeader.Set("Set-Cookie",
-		resp.Header.Get(http.CanonicalHeaderKey("Set-Cookie")))
+	if hdr := resp.Header.Get("Sec-Websocket-Protocol"); hdr != "" {
+		upgradeHeader.Set("Sec-Websocket-Protocol", hdr)
+	}
+	if hdr := resp.Header.Get("Set-Cookie"); hdr != "" {
+		upgradeHeader.Set("Set-Cookie", hdr)
+	}
 
 	// Now upgrade the existing incoming request to a WebSocket connection.
 	// Also pass the header that we gathered from the Dial handshake.