Singletons are not initialized

[IcedQuinn]

There is a bit of a goof. If singletons are enabled but have not yet been initialized then they are assigned to instance which is still nil. The code path to initialize the object is ignored.

I've fixed it with this patch.

diff --git a/lua-di.lua b/lua-di.lua
index bfa4a10..b606d5a 100644
--- a/lua-di.lua
+++ b/lua-di.lua
@@ -166,19 +166,20 @@ local dependency_injection_module = function(configure)
             instance = providers[module_name] 
         end
 
+        local module_handle = dynamic_require(module_name)
+        local module_constructor = get_constructor(module_name, module_handle)
+
+        -- new instance
+        instance = build_instance(module_constructor)
         if singletons[module_name] then
             -- initialise singleton instance if needed
             singletons[module_name].instance = instance
 
             -- singleton instance
             return singletons[module_name].instance
+        else
+            return instance
         end
-
-        local module_handle = dynamic_require(module_name)
-        local module_constructor = get_constructor(module_name, module_handle)
-
-        -- new instance
-        return build_instance(module_constructor)
     end
 
     return self