submodule对gitea不管用，所以直接拉了一份拉格兰

Lagrange.Core/Lagrange.OneBot/Utility/FallbackAsync.cs

@@ -0,0 +1,29 @@
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Lagrange.OneBot.Utility.Fallbacks;
+
+public class FallbackAsync
+{
+    private readonly List<Func<CancellationToken, Task<bool>>> _executors = [];
+
+    internal static FallbackAsync Create()
+    {
+        return new();
+    }
+
+    public FallbackAsync Add(Func<CancellationToken, Task<bool>> executor)
+    {
+        _executors.Add(executor);
+        return this;
+    }
+
+    public async Task<bool> ExecuteAsync(CancellationToken token = default)
+    {
+        foreach (var executor in _executors)
+        {
+            if (await executor(token)) return true;
+        }
+        return false;
+    }
+}