Check for a unity version

Author: sunnamed434

test/BitMono.Unity.TestProject/Assets/Scripts/GameManager.cs

@@ -35,7 +35,11 @@ public static GameManager Instance
         {
             if (instance == null)
             {
+#if UNITY_2020_1_OR_NEWER
                 instance = FindFirstObjectByType<GameManager>();
+#else
+                instance = FindObjectOfType<GameManager>();
+#endif
             }
             return instance;
         }