code: func (by By) Sort(jobs []*Job) {
  	js := &jobSorter{
  		jobs: jobs,
  		by:   by, // The Sort method's receiver is the function (closure) that defines the sort order.
  	}
  	sort.Sort(js)
  }
docs: // Sort is a method on the function type, By, that sorts the argument slice according to the function.