public class TestController : ApiController
{
    public Task<bool> Get(int count, CancellationToken cancellationToken)
    {
        return Task.Factory.StartNew(() =>
        {
            int i = 0;

            for (; count --> i ;)
            {
                cancellationToken.ThrowIfCancellationRequested();

                Thread.Sleep(10);
            }

            return true;
        }, cancellationToken);
    }
}