Load D shared library on windows x64

[Tofu Ninja via Digitalmars-d-learn]

Do shared libraries work? I am trying to load a D library into a 
D program but Runtime.loadLibrary just returns null for me and I 
am not sure what I am doing wrong.

import std.stdio;
import std.file : exists, getcwd, rename;
import core.thread;
import std.conv : to;
version(tofu_dynamic){
        import core.sys.windows.windows;
        import core.runtime;
        pragma(msg, "Dynamic Link Library");
        HINSTANCE g_hInst;
	export extern (Windows) BOOL DllMain(HINSTANCE hInstance, ULONG 
ulReason, LPVOID pvReserved) {
            switch (ulReason) {
                case DLL_PROCESS_ATTACH:
                    writeln("DLL_PROCESS_ATTACH");
                    Runtime.initialize();
                    break;

                case DLL_PROCESS_DETACH:
                    writeln("DLL_PROCESS_DETACH");
                    Runtime.terminate();
                    break;

                case DLL_THREAD_ATTACH:
                    writeln("DLL_THREAD_ATTACH");
                    return false;

                case DLL_THREAD_DETACH:
                    writeln("DLL_THREAD_DETACH");
                    return false;

                default:
            }
            g_hInst = hInstance;
            return true;
        }

        pragma(mangle, "rti_start") export void rti_start(){
                writeln("rti start :)");
        }

} else {
        void main(string[] args) {
                uint id = 0;

                while(true) {
                        if(exists("graph.dll")){
                                auto name = "rti." ~ id.to!string ~ ".dll";
                                rename("graph.dll", name);
                                id++;
                                loadLib(name);
                        }
                        Thread.sleep(dur!("seconds")(1));
                }
        }

        static void loadLib(string dllName) {
                import core.sys.windows.windows;
                import core.runtime;
                Thread.sleep(dur!("seconds")(1));
                writeln("Start Dynamic Link to ", dllName, "...");
                HMODULE h = cast(HMODULE) Runtime.loadLibrary(dllName);
                if (h is null) {
                        writeln("error loading");
                        return;
                }

                scope(exit){
                        if (!Runtime.unloadLibrary(h))
                                writeln("error freeing dll");
                }

                FARPROC fp = GetProcAddress(h, "rti_start");
                if (fp is null) {
                        writeln("error loading symbol rti_start");
                        return;
                }
                
                auto fun = cast(void function()) fp;
                fun();
                writeln("End...");
        }
}