async init() {
    const [storageInfo, cacheInfo] = await Promise.all([
      global.kuzzle.ask("core:storage:public:info:get"),
      global.kuzzle.ask("core:cache:public:info:get"),
    ]);
    this._info.elasticsearch = storageInfo;
    this._info.redis = cacheInfo;
  }
Init ServerController
Used to perform asynchronous initialization safely: the funnel will wait
for all controllers to be initialized before accepting requests.

@returns {Promise}