code: func (p *WebPage) EvaluateAsync(script string, delay time.Duration) error {
  	return p.ref.process.doJSON("POST", "/webpage/EvaluateAsync", map[string]interface{}{"ref": p.ref.id, "script": script, "delay": int(delay / time.Millisecond)}, nil)
  }
docs: // EvaluateAsync executes a JavaScript function and returns immediately.
  // Execution is delayed by delay. No value is returned.