Fix example output line

README.md

@@ -15,6 +15,6 @@ use std::time::Duration;
 
 fn my_cross_platform_timer(last_time: Spot) {
     let time_diff: Duration = Spot::now() - last_time;
-    println!("It has been {} seconds", time_diff.as_seconds());
+    println!("It has been {} seconds", time_diff.as_secs());
 }
 ```