code: func (r *regulator) Reader(ctx context.Context, path string, offset int64) (io.ReadCloser, error) {
  	r.enter()
  	defer r.exit()
  
  	return r.StorageDriver.Reader(ctx, path, offset)
  }
docs: // Reader retrieves an io.ReadCloser for the content stored at "path"
  // with a given byte offset.
  // May be used to resume reading a stream by providing a nonzero offset.