refactor: use addServerMiddleware (#44)

Author: ricardogobbosouza

lib/module.js

@@ -61,7 +61,7 @@ function proxyModule(options) {
     // https://github.com/chimurai/http-proxy-middleware
     const middleware = Proxy.apply(undefined, args)
     middleware.prefix = false // Don't add router base
-    this.options.serverMiddleware.push(middleware)
+    this.addServerMiddleware(middleware)
   })
 }