局部变量问题的微返行地址

Server function code:

func (s *service) CreateConsignment(ctx context.Context, req *pb.Consignment, resp *pb.Response) error {
consignment, err := s.repo.Create(req)
if err != nil {
    return err
}
resp = &pb.Response{Created: true, Consignment: consignment}
return nil

}

Client code:

resp, err := client.CreateConsignment(context.Background(),consignment)
if err != nil {
    log.Fatalf("create consignment error: %v", err)
}

But client's resp is:

{false <nil> [] {} [] 0}

the only way I can get it to work now is if to set resp in the server like this:

resp.Created = true
resp.Consignment = consignment

The issue here being:

resp = &pb.Response{Created: true, Consignment: consignment}

why is setting resp manually working but assigning it to the address of a new local variable doesn't?