MediatR 3.0.1 possible bug? Cannot get IAsyncRequestHandler working - asp.net-core

Question

I am getting the following error message when executing IRequest with IAsyncRequestHandler.
System.InvalidOperationException: 'No service for type 'MediatR.IRequestHandler`2[TestProject.Domain.Requests.Users.CreateUserRequest,TestProject.Domain.Requests.Users.CreateUserResponse]' has been registered.'
This is how i register it in the startup class
// Add framework services.
services.AddMvc();
services.AddMediatR(typeof(CreateUserRequest).GetTypeInfo().Assembly);
CreateUserRequest and Response
public class CreateUserRequest : IRequest<CreateUserResponse>
{
public string EmailAddress { get; set; }
public int OrganisationId { get; set; }
public string Password { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
public class CreateUserResponse
{
public int UserId { get; set; }
public string EmailAddress { get; set; }
}
Request handler
public class CreateUserRequestHandler : IAsyncRequestHandler<CreateUserRequest, CreateUserResponse>
{
private readonly UserManager<User> _userManager;
public CreateUserRequestHandler()
{
}
public async Task<CreateUserResponse> Handle(CreateUserRequest request)
{
//create the user and assign it to the organisation
var user = new User
{
Email = request.EmailAddress,
OrganisationUsers = new List<OrganisationUser> { new OrganisationUser { OrganisationId = request.OrganisationId } }
};
//create new user with password.
await _userManager.CreateAsync(user, request.Password);
//create response.
var response = new CreateUserResponse{UserId = user.Id, EmailAddress = user.Email};
return response;
}
}
Controller class
public class UserController : Controller
{
private readonly IMediator _mediator;
public UserController(IMediator mediator)
{
_mediator = mediator;
}
[HttpPost]
public async Task<CreateUserResponse> Post(CreateUserRequest request)
{
return await _mediator.Send(request);
}
}
the error occurs inside the controller class it does not hit the async request handler.
Is there anything wrong with the DI registration? I have looked at the examples but could not find anything specific to aspnet core.