code: public function config($configurator)
  	{
  		if ($this->booted) {
  			$this->invokeConfigurator($configurator);
  		} else {
  			$this->configurators->push($configurator);
  		}
  	}
docs: Push a configurator on top of the stack. The configurators will be
  executed when the application is booted. If the application is already
  booted, the configurator will be executed at once.
  
  @param  callable|string|ConfiguratorInterface $configurator
  
  @return void