AsyncExtensions.cs

using System.Threading.Tasks;
using UnityEngine;

public static class AsyncExtensions
{
    public static Task GetTask(this AsyncOperation asyncOp)
    {
        TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();
        asyncOp.completed += _ => tcs.SetResult(null);
        return tcs.Task;
    }
}