ctx, span := trace.StartSpan(ctx, "load.TestPackagesAndErrors")
	defer span.Done()

	pre := newPreload()
	defer pre.flush()
	allImports := append([]string{}, p.TestImports...)
	allImports = append(allImports, p.XTestImports...)
	pre.preloadImports(ctx, opts, allImports, p.Internal.Build)

// modified by modload.LoadPackages.
type preload struct {
	cancel chan struct{}
	sema   chan struct{}
}

// newPreload creates a new preloader. flush must be called later to avoid
// accessing global state while it is being modified.
func newPreload() *preload {
	pre := &preload{
		cancel: make(chan struct{}),
		sema:   make(chan struct{}, preloadWorkerCount),
	}
	return pre
}