code: func (c *BundlingChecker) Close() error {
  	c.bundler.Flush()
  	c.wg.Wait()
  	close(c.waitc) // Sanity check that we don't do any more checks.
  
  	// After Close has returned, we know there are no outstanding running
  	// checks.
  	return c.err
  }
docs: // Close shuts down the checker, blocking until all pending items have been
  // checked with the server. Close returns the first error encountered during
  // the checking process, if any.
  // After Close has returned, Checker is guaranteed to no longer invoke any
  // previously-provided callback.