source: https://stackoverflow.com/questions/57313252/how-can-i-await-an-array-of-tasks-and-stop-waiting-on-first-exception/57313477#57313477

FailFastWhenAll.cs

public static class TaskExtentions
{
    public static Task<TResult[]> WhenAllFailFast<TResult>(IEnumerable<Task<TResult>> tasks)
    {
        return WhenAllFailFast(tasks.ToArray());
    }
    public static Task<TResult[]> WhenAllFailFast<TResult>(params Task<TResult>[] tasks)
    {
        if (tasks is null) throw new ArgumentNullException(nameof(tasks));
        if (tasks.Length == 0) return Task.FromResult(new TResult[0]);

        var results = new TResult[tasks.Length];
        var remaining = tasks.Length;
        var tcs = new TaskCompletionSource<TResult[]>(
            TaskCreationOptions.RunContinuationsAsynchronously);

        for (int i = 0; i < tasks.Length; i++)
        {
            var task = tasks[i];
            if (task == null) throw new ArgumentException(
                $"The {nameof(tasks)} argument included a null value.", nameof(tasks));
            HandleCompletion(task, i);
        }
        return tcs.Task;

        async void HandleCompletion(Task<TResult> task, int index)
        {
            try
            {
                var result = await task.ConfigureAwait(false);
                results[index] = result;
                if (Interlocked.Decrement(ref remaining) == 0)
                {
                    tcs.TrySetResult(results);
                }
            }
            catch (OperationCanceledException)
            {
                tcs.TrySetCanceled();
            }
            catch (Exception ex)
            {
                tcs.TrySetException(ex);
            }
        }
    }
    public static Task WhenAllFailFast(IEnumerable<Task> tasks)
    {
        return WhenAllFailFast(tasks.ToArray());
    }
    public static Task WhenAllFailFast(params Task[] tasks)
    {
        if (tasks is null) throw new ArgumentNullException(nameof(tasks));
        if (tasks.Length == 0) return Task.CompletedTask;

        var remaining = tasks.Length;
        var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);

        for (int i = 0; i < tasks.Length; i++)
        {
            var task = tasks[i];
            if (task == null) throw new ArgumentException(
                $"The {nameof(tasks)} argument included a null value.", nameof(tasks));
            HandleCompletion(task, i);
        }
        return tcs.Task;

        async void HandleCompletion(Task task, int index)
        {
            try
            {
                await task.ConfigureAwait(false);
                if (Interlocked.Decrement(ref remaining) == 0)
                {
                    tcs.TrySetResult(true);
                }
            }
            catch (OperationCanceledException)
            {
                tcs.TrySetCanceled();
            }
            catch (Exception ex)
            {
                tcs.TrySetException(ex);
            }
        }
    }
}