code: func expireBuild(c context.Context, b *buildbot.Build) error {
  	if !b.TimeStamp.IsZero() {
  		b.Times.Finish = b.TimeStamp
  	} else {
  		b.Times.Finish.Time = clock.Now(c)
  	}
  	b.Finished = true
  	b.Results = buildbot.Exception
  	b.Currentstep = nil
  	b.Text = append(b.Text, "Build expired on Milo")
  	_, err := SaveBuild(c, b)
  	return err
  }
docs: // expireBuild marks a build as finished and expired.