Async task request

how to create a task request (mail webservice) in order to not wait for response and continue code execution, like:

class HomePageHandler implements RequestHandlerInterface{

    public function handle(ServerRequestInterface $request): ResponseInterface
    {

	    $_post = $request->getParsedBody();

		if( isset($_post['email']) ){
			/**
			 * send async request and do not wait it!
			 */
			
  		    $client = new Client();
			$client->setUri("https://mail-api-srv:9501/api/mail");
			$client->setMethod("GET");
			$client->setParameterGet(['mail'=>$_post['mail'],'action'=>'recoveryAccount']);
			$responseMail = $client->send();
			
			// no need get body
			#$body = $responseMail->getBody();
		}

	    // continue code execution, do not wait response from MAIL API
	    
	    // Example
	    // save user action into DB
	    $this->tableGateway->save(
			[
				'mail'=>$_post,
				'action'=>'recoveryAccount'
			]
	    );
		
		// return message to user, and mail microservice is processing the request 
		
	    return new JsonResponse(['message'=>'Check your inbox/spam folder'],200);
    }
	

}