Producer-Consumer problem implementation

ProducerConsumer.cs

using System;
using System.Threading;

class Program
{
    static int prodIndex = 0;
    static int consIndex = 0;
    static Semaphore empty, filled;
    static string[] buffer;

    static void Main(string[] args)
    {
        var prod1 = new Thread(Producer);
        var cons1 = new Thread(Consumer);

        buffer = new string[20];
        empty = new Semaphore(buffer.Length, buffer.Length);
        filled = new Semaphore(0, buffer.Length);

        prod1.Start();
        cons1.Start();

        Thread.Sleep(100000);
    }

    static void Producer()
    {
        var id = Thread.CurrentThread.ManagedThreadId;
        for (var cnt = 0; ;)
        {
            var item = $"{id} @ {++cnt}";
            empty.WaitOne();

            var i = Interlocked.Increment(ref prodIndex);
            i = (i - 1) % buffer.Length;
            buffer[i] = item;

            filled.Release();

            Thread.Sleep(500);
        }
    }

    static void Consumer()
    {
        var id = Thread.CurrentThread.ManagedThreadId;
        while (true)
        {
            filled.WaitOne();

            var i = Interlocked.Increment(ref consIndex);
            i = (i - 1) % buffer.Length;
            var item = buffer[i];

            empty.Release();

            Console.WriteLine($"{id} <-- {item}");
        }
    }
}