code: func (c *BundlingChecker) check(items []checkerItem) {
  	c.waitc <- struct{}{}
  	c.wg.Add(1)
  	go func() {
  		c.doCheck(items)
  		c.wg.Done()
  		<-c.waitc
  	}()
  
  }
docs: // check is invoked from the bundler's handler.
  // It launches a check in a new goroutine. Any error is communicated via c.err