core/Controller.php
public function getSession(string $name = null, $def = null)
    {
        return Request::getSession($name, $def);
    }
public function getSession(string $name = null, $def = null)
    {
        return Request::getSession($name, $def);
    }
获取 session 相当于 $_SESSION[$name]
@param string|null $name
@param null $def
@return null