code: func (l *JSONFileLogger) Close() error {
  	l.mu.Lock()
  	l.closed = true
  	err := l.writer.Close()
  	for r := range l.readers {
  		r.ProducerGone()
  		delete(l.readers, r)
  	}
  	l.mu.Unlock()
  	return err
  }
docs: // Close closes underlying file and signals all the readers
  // that the logs producer is gone.