Port of Polly library for Unity based on UniTask

This version is based of v7.2.4 of the Polly library as it has no external dependancies on netstandard 2.1 which is perfect for Unity.

Example of Retry policy combined with a Fallback (by PolicyWrap):

using Cysharp.Threading.Tasks;
using Polly;
using System;
using UnityEngine;
using UnityEngine.Networking;

public class Retry : MonoBehaviour
{
    async void Start()
    {
        var retry = Policy
            .Handle<Exception>()
            .RetryAsync(3, onRetry: (Exception ex, int retryCount) =>
            {
                Debug.Log($"{ex.Message} Retry: " + retryCount);
            });

        // in real world scenario:
        //var retryWebRequest = Policy
        //    .HandleResult<UnityWebRequest>(x => x.result == UnityWebRequest.Result.ConnectionError)
        //    .RetryAsync(3, onRetry: (x, retryCount) =>
        //    {
        //        Debug.Log($"Retry: " + retryCount);
        //    });        

        var fallback = Policy<string>
            .Handle<Exception>()
            .FallbackAsync("MIT ");

        var policy = fallback.WrapAsync(retry);

        var license = await policy.ExecuteAsync(FetchLicense);

        Debug.Log(license);
    }

    async UniTask<string> FetchLicense()
    {
        if (UnityEngine.Random.value < 0.8f)
        {
            throw new Exception("Failed to fetch license");
        }

        var request = UnityWebRequest.Get("https://www.boost.org/LICENSE_1_0.txt");
        await request.SendWebRequest();
        return request.downloadHandler.text;
    }
}

To install in Unity project use this UPM link: https://github.com/slimshader/Unity.Polly.git?path=Packages/Unity.Polly