import from UniRx and some modified.

Assets/UniRx.Async/Internal/Hack.cs

@@ -0,0 +1,23 @@
+#if NET_4_6 || NET_STANDARD_2_0 || CSHARP_7_OR_LATER
+
+using System;
+
+namespace UniRx.Async.Internal
+{
+    internal static class FuncExtensions
+    {
+        // avoid lambda capture
+
+        internal static Action<T> AsFuncOfT<T>(this Action action)
+        {
+            return new Action<T>(action.Invoke);
+        }
+
+        static void Invoke<T>(this Action action, T unused)
+        {
+            action();
+        }
+    }
+}
+
+#endif