Use callback properly

app.js

@@ -133,12 +133,13 @@ process.on('SIGTERM', function () {
                 }
 
                 global.logger.info('Exit gracefully');
-                server.batch.logger.end();
+                server.batch.logger.end(function () {
                     process.exit(0);
                 });
             });
         });
     });
+});
 
 function isGteMinVersion(version, minVersion) {
     var versionMatch = /[a-z]?([0-9]*)/.exec(version);

app/services/logger.js

@@ -56,13 +56,13 @@ class Logger {
     //
     // See: https://github.com/trentm/node-bunyan/issues/37
     // See: https://github.com/trentm/node-bunyan/issues/73
-    end () {
+    end (callback) {
         // process.stdout cannot be closed
         if (!this.path) {
-            return;
+            return callback();
         }
 
-        this.logger.streams[0].stream.on('finish', resolve);
+        this.logger.streams[0].stream.on('finish', callback);
         this.logger.streams[0].stream.end(); // close stream, flush buffer to disk
     }
 }