Program.cs

using System;
using System.Threading;
using System.Threading.Tasks;
using _03_sharded_client.Services;
using Discord;
using Discord.Commands;
using Discord.WebSocket;
using Microsoft.Extensions.DependencyInjection;

namespace _03_sharded_client
{
    // This is a minimal example of using Discord.Net's Sharded Client
    // The provided DiscordShardedClient class simplifies having multiple
    // DiscordSocketClient instances (or shards) to serve a large number of guilds.
    class Program
    {
        static void Main(string[] args)
            => new Program().MainAsync().GetAwaiter().GetResult();
        public async Task MainAsync()
        {
            // You specify the amount of shards you'd like to have with the
            // DiscordSocketConfig. Generally, it's recommended to
            // have 1 shard per 1500-2000 guilds your bot is in.
            var config = new DiscordSocketConfig
            {
                TotalShards = 2
            };

            // You should dispose a service provider created using ASP.NET
            // when you are finished using it, at the end of your app's lifetime.
            // If you use another dependency injection framework, you should inspect
            // its documentation for the best way to do this.
            using (var services = ConfigureServices(config))
            {
                var client = services.GetRequiredService<DiscordShardedClient>();

                // The Sharded Client does not have a Ready event.
                // The ShardReady event is used instead, allowing for individual
                // control per shard.
                client.ShardReady += ReadyAsync;

                await services.GetRequiredService<CommandHandlingService>().InitializeAsync();

                // Tokens should be considered secret data, and never hard-coded.
                await client.LoginAsync(TokenType.Bot, Environment.GetEnvironmentVariable("token"));
                await client.StartAsync();

                await Task.Delay(Timeout.Infinite);
            }
        }

        private ServiceProvider ConfigureServices(DiscordSocketConfig config)
        {
            return new ServiceCollection()
                .AddSingleton(new DiscordShardedClient(config))
                .AddSingleton<CommandService>()
                .AddSingleton<CommandHandlingService>()
                .BuildServiceProvider();
        }


        private Task ReadyAsync(DiscordSocketClient shard)
        {
            Console.WriteLine($"Shard Number {shard.ShardId} is connected and ready!");
            return Task.CompletedTask;
        }
    }
}