Add some lock.

src/Aiursoft.ChessServer/Controllers/GamesController.cs

@@ -78,21 +78,16 @@ public class GamesController : Controller
     public async Task<IActionResult> Move([FromRoute] int id, [FromRoute] string player, [FromRoute] string move)
     {
         var game = _database.GetOrAddGame(id);
-        try
+        lock (game.MovePieceLock)
         {
             if (!game.Board.IsValidMove(move) || game.Board.IsEndGame || game.Board.Turn.AsChar.ToString() != player)
             {
                 return BadRequest();
             }
-
             game.Board.Move(move);
-            var fen = game.Board.ToFen();
-            await Task.WhenAll(game.Channel.Broadcast(fen));
-            return Ok(fen);
-        }
-        catch
-        {
-            return BadRequest();
         }
+        var fen = game.Board.ToFen();
+        await Task.WhenAll(game.Channel.Broadcast(fen));
+        return Ok(fen);
     }
 }

src/Aiursoft.ChessServer/Data/InMemoryDatabase.cs

@@ -16,7 +16,10 @@ public class InMemoryDatabase : ISingletonDependency
 
     public Game GetOrAddGame(int id)
     {
-        return Games.GetOrAdd(id, _ => new Game());
+        lock (this)
+        {
+            return Games.GetOrAdd(id, _ => new Game());
+        }
     }
 }
 

src/Aiursoft.ChessServer/Models/Game.cs

@@ -7,5 +7,7 @@ public class Game
 {
     public ChessBoard Board { get; set; } = new();
 
-    public AsyncObservable<string> Channel { get; set; } = new ();
+    public AsyncObservable<string> Channel { get; set; } = new();
+    
+    public object MovePieceLock { get; } = new();
 }

src/Aiursoft.ChessServer/Models/Message.cs

@@ -1,11 +0,0 @@
-namespace Aiursoft.ChessServer.Models;
-
-public class Message
-{
-    public Message(string content)
-    {
-        Content = content;
-    }
-
-    public string Content { get; set; }
-}