Simple C# Task based state machine

StateMachine.cs

using System;
using System.Threading.Tasks;

public interface IState
{
    Task RunAsync();
}

public class StateMachine
{
    private Task currentTask = Task.CompletedTask;

    public void SetState<T>() where T : IState, new()
    {
        Task.Run(() =>
        {
            currentTask.ContinueWith(_ => currentTask = new T().RunAsync() );
        }).FireAndForget();
    }
}

public static class TaskExtensions
{
    public static void FireAndForget(this Task task) => task?.ContinueWith(t => GC.KeepAlive(t.Exception), TaskContinuationOptions.OnlyOnFaulted);
}