adding response post-processing middleware example

Author: jkyberneees

demos/before-end-middleware.js

@@ -0,0 +1,28 @@
+'use strict'
+
+const gateway = require('./../index')
+const PORT = process.env.PORT || 8080
+
+const middleware503to404 = (req, res, next) => {
+  const end = res.end
+  res.end = function (...args) {
+    if (res.statusCode === 503) {
+      res.statusCode = 404
+    }
+    return end.apply(res, args)
+  }
+
+  return next()
+}
+
+gateway({
+  routes: [{
+    prefix: '/service',
+    target: 'http://127.0.0.1:3000',
+    middlewares: [
+      middleware503to404
+    ]
+  }]
+}).start(PORT).then(server => {
+  console.log(`API Gateway listening on ${PORT} port!`)
+})