Inital commit

.gitignore

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+bin
+obj
+.vs

Contracts/What.cs

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+using System.Threading.Tasks;
+
+namespace DotWhat.Contracts
+{
+    public abstract class What
+    {
+        public abstract string Name { get; }
+
+        public abstract Task RunAsync();
+    }
+}

DotWhat.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Cocona.Lite" Version="1.5.0" />
+  </ItemGroup>
+
+</Project>

DuckTyping/CustomAwaiters.cs

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+using DotWhat.Contracts;
+using System;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+
+namespace DotWhat.DuckTyping
+{
+    public sealed class CustomAwaiters : What
+    {
+        public override string Name => "CustomAwaiters";
+
+        public override async Task RunAsync()
+        {
+            int i = 123;
+
+            Console.WriteLine(await (await await 7 + await i));
+        }
+    }
+
+    public static class IntExtensions
+    {
+        public static IntAwaiter GetAwaiter(this int i) => new IntAwaiter(i);
+    }
+
+    public sealed class IntAwaiter : INotifyCompletion
+    {
+        private readonly int _value;
+        public bool IsCompleted => true;
+
+        public IntAwaiter(int i) => _value = i;
+
+        public int GetResult() => _value;
+
+        public void OnCompleted(Action continuation)
+        {
+        }
+    }
+}

Program.cs

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+using DotWhat.Contracts;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Threading.Tasks;
+using Cocona;
+
+namespace DotWhat
+{
+    class Program
+    {
+        private static readonly IEnumerable<What> Whats =
+            Assembly.GetExecutingAssembly()
+                .GetTypes()
+                .Where(type => type.BaseType == typeof(What))
+                .Select(what => (What)Activator.CreateInstance(what));
+
+        private static async Task<int> Main(string[] args)
+        {
+            await CoconaLiteApp.RunAsync<Program>(args);
+
+            return 0;
+        }
+
+        public async Task StartAsync([Argument] string name = default)
+        {
+            if (string.IsNullOrEmpty(name))
+            {
+                Console.WriteLine("No what passed. Current available whats are:");
+                PrintWhats();
+                return;
+            }
+
+            var command = Whats.FirstOrDefault(what => what.Name.Equals(name, StringComparison.OrdinalIgnoreCase));
+
+            if (command is null)
+            {
+                Console.WriteLine("Invalid what passed. Current available whats are:");
+                PrintWhats();
+                return;
+            }
+
+            await command.RunAsync();
+
+            static void PrintWhats()
+                => Whats.ToList().ForEach(what => Console.WriteLine(what.Name.ToLower()));
+        }
+    }
+}