Magento 2 – Fatal Error: Uncaught TypeError: Argument 1 Passed

Please anyone see my code and resolve this issue

Fatal error: Uncaught TypeError: Argument 1 passed to
MyClass::__construct() must implement interface
Magento\Framework\Session\SessionManagerInterface, none given, called
in
/home/dukaania/public_html/testing2/vendor/magento/module-checkout/view/frontend/templates/cart/shipping.phtml
on line 132 and defined in
/home/dukaania/public_html/testing2/vendor/magento/module-checkout/view/frontend/templates/cart/shipping.phtml:109
Stack trace: #0

    use Magento\Framework\Session\SessionManagerInterface as CoreSession;

    class MyClass
    {

        protected $_coreSession;

        public function __construct(CoreSession $coreSession) 
        {
            $this->_coreSession = $coreSession;

        }

      public function setValue($total_cost){
        $this->_coreSession->start();
        $this->_coreSession->setMessage($total_cost);


    }

    public function getValue(){
        $this->_coreSession->start();
        return $this->_coreSession->getMessage();


    }


}

$myclas = new MyClass();

 $myclas.setValue($total_cost);     
 echo $myclas.getValue();