Refactoring to asynchronous. (partially completed)

MinecraftClient/AsyncTaskHandler.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using MinecraftClient.Protocol.ProfileKey;
+using MinecraftClient.Protocol.Session;
+
+namespace MinecraftClient
+{
+    internal static class AsyncTaskHandler
+    {
+        private static readonly List<Task> Tasks = new();
+
+        internal static Task CheckUpdate = Task.CompletedTask;
+
+        internal static Task CacheSessionReader = Task.CompletedTask;
+
+        internal static Task SaveSessionToDisk = Task.CompletedTask;
+
+        internal static Task WritebackSettingFile = Task.CompletedTask;
+
+        internal static async void ExitCleanUp()
+        {
+            await WritebackSettingFile;
+
+            await CacheSessionReader;
+
+            await SaveSessionToDisk;
+
+            foreach (var task in Tasks)
+            {
+                await task;
+            }
+
+            Tasks.Clear();
+        }
+    }
+}