rename get_instance function

bin/utils/main.cpp

@@ -94,7 +94,7 @@ auto main(int argc, char *argv[]) -> int
   }
 
   {// ex: singleton
-    test_singleton::get_instance().print();
+    test_singleton::instance().print();
   }
 }
 

src/hack/utils/singleton.hpp

@@ -19,7 +19,7 @@ namespace hack::utils
   template<typename T>
   struct singleton : public no_move, no_copy
   {
-    static T& get_instance()
+    static T& instance()
     {
       static T t;
       return t;