add tokio::time::pause to msim

Author: aschran

msim/src/sim/time/mod.rs

@@ -246,12 +246,16 @@ where
     }
 }
 
-/// Supply tokio::time::advance() API (for compilation only - this method
-/// is meaningless inside the simulator).
+/// Supply tokio::time::advance() and tokio::time::pause() APIs (for compilation only -
+/// these methods are meaningless inside the simulator).
 pub async fn advance(_duration: Duration) {
     unimplemented!("cannot advance clock in simulation - use sleep() instead");
 }
 
+pub fn pause() {
+    unimplemented!("cannot pause clock in simulation");
+}
+
 /// Require a `Future` to complete before the specified duration has elapsed.
 pub fn timeout<T: Future>(duration: Duration, future: T) -> Timeout<T> {
     let handle = TimeHandle::current();