How to get back Task<int> of a function (Mediatr) - Asp.net Core MVC

Question

How do I get the entire value returned through a Task? I have tried several ways, as I have seen in forums on the net, but I could not. I tried to use var customerId = Bus.Sendcommand(registerCommand). Result, but it doesn’t work... Thank you all :)

public class CustomerCommandHandler : CommandHandler,
    IRequestHandler<RegisterNewCustomerCommand, int>,       
{
    private readonly ICustomerRepository _customerRepository;
    private readonly IMediatorHandler Bus;

    public CustomerCommandHandler(ICustomerRepository customerRepository, 
                                  IUnitOfWork uow,
                                  IMediatorHandler bus,
                                  INotificationHandler<DomainNotification> notifications) :base(uow, bus, notifications)
    {
        _customerRepository = customerRepository;
        Bus = bus;
    }

    public Task<int> Handle(RegisterNewCustomerCommand message, CancellationToken cancellationToken)
    {
        if (!message.IsValid())
        {
            NotifyValidationErrors(message);
            return Task.FromResult(0);
        }

        var customer = new Customer(Guid.NewGuid(), message.Name, message.Email, message.BirthDate);

        if (_customerRepository.GetByEmail(customer.Email) != null)
        {
            Bus.RaiseEvent(new DomainNotification(message.MessageType, "The customer e-mail has already been taken."));
            return Task.FromResult(0);
        }

        _customerRepository.Add(customer);

        if (Commit())
        {
            Bus.RaiseEvent(new CustomerRegisteredEvent(customer.Id, customer.Name, customer.Email, customer.BirthDate));
        }

        return Task.FromResult(customer.Id);
    }

    public void Dispose()
    {
        _customerRepository.Dispose();
    }
}

Calling for:

 public void Register(CustomerViewModel customerViewModel)
{
    var registerCommand = _mapper.Map<RegisterNewCustomerCommand>(customerViewModel);
    var customerId = Bus.SendCommand(registerCommand); /////????????????????????
}