Adding asyncMiddleware.

package.json

@@ -22,6 +22,7 @@
     "assets/style.css"
   ],
   "dependencies": {
+    "async": "^3.2.0",
     "body-parser": "^1.19.0",
     "decache": "^4.6.0",
     "express-http-proxy": "^1.6.2"
@@ -29,6 +30,7 @@
   "devDependencies": {
     "@purtuga/esm-webpack-plugin": "^1.1.1",
     "@tsconfig/node12": "^1.0.7",
+    "@types/async": "^3.2.6",
     "@types/express": "^4.17.11",
     "@types/express-http-proxy": "^1.6.1",
     "@types/node": "^14.14.37",