Update src/lib.rs

Co-authored-by: Leonardo L. <[email protected]>

Author: praveenperera

src/lib.rs

@@ -1025,7 +1025,7 @@ mod test {
     #[cfg(all(feature = "async", not(feature = "tokio")))]
     struct TestRuntime;
 
-    #[cfg(not(feature = "tokio"))]
+    #[cfg(all(feature = "async", not(feature = "tokio")))]
     impl Sleeper for TestRuntime {
         async fn sleep(duration: Duration) {
             tokio::time::sleep(duration).await;