Fixed header tool user agent rewrite seq

mod/dynamicproxy/dpcore/dpcore.go

@@ -295,12 +295,12 @@ func (p *ReverseProxy) ProxyHTTP(rw http.ResponseWriter, req *http.Request, rrr
 	// Add X-Forwarded-For Header.
 	addXForwardedForHeader(outreq)
 
-	// Rewrite outbound UA
-	rewriteUserAgent(outreq.Header, "Zoraxy/"+rrr.Version)
-
 	// Add user defined headers (to upstream)
 	injectUserDefinedHeaders(outreq.Header, rrr.UpstreamHeaders)
 
+	// Rewrite outbound UA, must be after user headers
+	rewriteUserAgent(outreq.Header, "Zoraxy/"+rrr.Version)
+
 	res, err := transport.RoundTrip(outreq)
 	if err != nil {
 		if p.Verbal {