fix sslify with heroku

src/app.ts

@@ -7,6 +7,7 @@ import * as jwt from "koa-jwt";
 import * as logger from "koa-logger";
 import * as send from "koa-send";
 import sslify from "koa-sslify";
+import { xForwardedProtoResolver } from "koa-sslify";
 import * as serve from "koa-static";
 
 import { config, EnvType } from "~config";
@@ -19,7 +20,7 @@ app.use(cors());
 app.use(logger());
 app.use(bodyParser());
 if (config.env === EnvType.production) {
-    app.use(sslify());
+    app.use(sslify({ resolver: xForwardedProtoResolver }));
 }
 app.use(
     jwt({