custom options – How can I get customer data in a plugin class?

I’m trying to access logged in customer data in an “after” plugin.

The plugin is working, but I need some logic based on a custom customer attribute.

I try to do this but I get an error

Fatal error: Uncaught Error: Call to a member function get() on null in /Users/name/file/project/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php on line 170

I’ve tried using create instead of get for the object manager, but I get the same result.

I have a helper function that I use to get this data in some phtml files, but it doesn’t seem to work in this class.

Do I have to get this data from somewhere else?

Thanks

namespace <company>EmailCopyPlugin;

use MagentoFrameworkAppObjectManager;
use MagentoSalesModelOrderEmailContainerOrderIdentity;
use PsrLogLoggerInterface;

class SendOrderCopy
{

   private $logger;
   private $objectManager;

   public function __construct(
       LoggerInterface $logger,
       ObjectManager $objectManager

   )
   {
       $this->logger = $logger;
       $this->objectManager = $objectManager;
   }

   public function afterGetEmailCopyTo(OrderIdentity $identity, $emailList)
   {
       $customer = $this->objectManager::getInstance()->get('MagentoCustomerModelSession')->getCustomer();
       $customer = $customer->getData();
       var_dump($customer);
       $emailList() = "<email>";
       $emailList() = "<email";
       return $emailList;
   }
}