IHostedService com Timer

timer.cs

public class ContractUpdated : IHostedService, IDisposible
{
    private Timer _timer;

    public Task StartAsync(CancellationToken token)
    {
        _timer = new Timer(
            UpdateContracts,
            null,
            TimeSpan.Zero, 
            TimeSpan.FromMinutes(60))

        return Task.CompletedTask;
    }

    private void UpdateContracts(object state)
    {
        // Executando um código muito demorado
        Thread.Sleep(5000);
    }

    public Task StopAsync(CancellationToken token)
    {
        _timer?.Change(Timeout.Infinite, 0);

        return Task.CompletedTask;
    }

    public void Dispose()
    {
        _timer?.Dispose();
    }
}