diff --git a/lib/application.js b/lib/application.js
index 8e3b82adf..7dec2b44d 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -47,6 +47,9 @@ class Application extends EggApplication {
     options.type = 'application';
     super(options);
 
+    // will auto set after 'server' event emit
+    this.server = null;
+
     try {
       this.loader.load();
     } catch (e) {
@@ -85,6 +88,9 @@ class Application extends EggApplication {
   }
 
   onServer(server) {
+    // expose app.server
+    this.server = server;
+
     /* istanbul ignore next */
     graceful({
       server: [ server ],
diff --git a/package.json b/package.json
index 222a0c592..c24254f8c 100644
--- a/package.json
+++ b/package.json
@@ -78,7 +78,7 @@
     "spy": "^1.0.0",
     "supertest": "^3.0.0",
     "ts-node": "^3.0.6",
-    "typescript": "^2.3.4",
+    "typescript": "^3.4.1",
     "webstorm-disable-index": "^1.1.2"
   },
   "main": "index.js",