example

src/main.rs

@@ -54,6 +54,8 @@ fn main() {
         u2.enter(&s, "abc"); //
         u2.user2(&s, &mut u1); // try with key set
         u2.user2(&s, &mut u1); // try with key set
+        u2.expire(&s);
+        u2.user2(&s, &mut u1); // try with key set
     };
 }