v6.1: TRunnable can be an interface

Now you can call AddTask on interface (inherited from IRunnable) and register it's implementation later manually. This may be useful when you have several versions of same task and need to choose correct one on startup depending on configuration.

services.AddTask<IFileProcessorTask>(o => o.AutoStart(TimeSpan.FromMinutes(1)));

switch (configuration["FileProcessingMode"])
{
  case "Network":
    services.AddTransient<IFileProcessorTask, NetworkFileProcessorTask>();
    break;
  default:
    services.AddTransient<IFileProcessorTask, LocalFileProcessorTask>();
    break;
}