If HTTP 1.1 is used and backend doesn't return 'Connection' header, explicitly

return Connection: keep-alive.

Author: Kami

lib/node-http-proxy/http-proxy.js

@@ -236,7 +236,14 @@ HttpProxy.prototype.proxyRequest = function (req, res, buffer) {
     //
     if (response.headers.connection) {
       if (req.headers.connection) { response.headers.connection = req.headers.connection }
-      else { response.headers.connection = 'close' }
+      else {
+        if (req.httpVersion === '1.0') {
+          response.headers.connection = 'close'
+        }
+        else if (req.httpVersion === '1.1') {
+          response.headers.connection = 'keep-alive'
+        }
+      }
     }
 
     // Remove `Transfer-Encoding` header if client's protocol is HTTP/1.0