Example fix - should be no const qualifier

README.md

@@ -21,7 +21,7 @@ int main(void)
 
     Server svr;
 
-    svr.get("/hi", [](const Request& req, const Response& res) {
+    svr.get("/hi", [](const Request& req, Response& res) {
         res.set_content("Hello World!", "text/plain");
     });