Async Rate Limiting with SemaphoreSlim

Program.cs

using System;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp3
{
    class Program
    {
        private const int RateLimit = 5;
        private static readonly Random _rng = new Random();
        private static readonly SemaphoreSlim _rateLimiter = new SemaphoreSlim(RateLimit, RateLimit);

        static void Main(string[] args)
        {
            const int NumTasks = 20;

            var tasks = Enumerable.Range(1, NumTasks)
                .Select(i => DoRateLimitedWork(i.ToString()))
                .ToArray();

            Task.WaitAll(tasks);

            if (Debugger.IsAttached)
            {
                Console.WriteLine("Done");
                Console.ReadKey(true);
            }
        }

        private static async Task DoRateLimitedWork(string name)
        {
            await _rateLimiter.WaitAsync();

            try
            {
                await DoSomeWork(name);
            }
            finally
            {
                _rateLimiter.Release();
            }
        }


        private static async Task DoSomeWork(string workName)
        {
            var delay = _rng.Next(500, 3000);
            Console.WriteLine($"Started {workName} for {delay}ms");
            await Task.Delay(TimeSpan.FromMilliseconds(delay));
            Console.WriteLine($"Ended {workName}");
        }
    }
}