message: selfCache getter overwriting with default when already defined issue
  the cache is always reset to default on subsequent get after getting it the first time
diff: @@ -1186,6 +1186,8 @@ export class GraphQLModule<
  } else {
  this._cache.selfKeyValueCache = null;
  }
  + } else {
  + cache = this._cache.selfKeyValueCache;
  }
  return cache;
  }
  