@Override
        public String toString() {
            return MoreObjects.toStringHelper(this)
                              .add("dirPath", dirPath)
                              .add("watchable", watchKey.watchable())
                              .add("isValid", watchKey.isValid())
                              .toString();
        }
Initializes the context for each watched path.
@param watchKey the {@link WatchKey} registered for the current path
@param callback the callback which is invoked on a watch event
@param dirPath path which is watched
core/src/main/java/com/linecorp/armeria/client/endpoint/FileWatcherRunnable.java