Singleton unique_ptr., C++ (vc++)

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#include <iostream>
#include <memory> // For unique_ptr.

using namespace std;

class Singleton {
public:
    static Singleton &getInstance( )
    {
        if (instance == nullptr) {
            cout << "Creating instance.\n";
            instance.reset(new Singleton()); // Create new instance, assign to unique_ptr.
        }
        return *instance;
    }
    static void destroyInstance()
    {
        if (instance != nullptr) {
            cout << "Destroying instance.\n";
            instance.reset(nullptr); // Replaces stored pointer with nullptr, calls deleter on pointed-to instance.
        }
    }

~Singleton( )
    {
        std::cout << "Destructor called.\n";
        if (instance == nullptr) {
            std::cout << "* Instance already deleted!\n";
        }
    }
private:
    Singleton( ) { }

// Custom deleter for unique_ptr.  Not actually required.
    static void destroy(Singleton* instance) {
        if (instance != nullptr) {
            cout << "Deleting...\n";
            delete instance;
            instance = nullptr;
        }
    }

// This version lets you specify a deleter, which must be callable with the stored pointer as its only parameter.
    //static std::unique_ptr<Singleton, decltype(&Singleton::destroy)> instance;
    
    // This version just uses delete to destroy the pointer.
    static std::unique_ptr<Singleton> instance;
};
//std::unique_ptr<Singleton, decltype(&Singleton::destroy)> Singleton::instance = {nullptr, &Singleton::destroy};
std::unique_ptr<Singleton> Singleton::instance = nullptr;

int main( )
{
    Singleton &singleton = Singleton::getInstance();

//    singleton.destroyInstance();

return 0;
}

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Compilation time: 1,68 sec, absolute running time: 0,23 sec, absolute service time: 1,92 sec