Use multi-worker scheduled executor

Co-authored-by: brunoborges <129743+brunoborges@users.noreply.github.com>

Author: Copilot

content/concurrency/timer-task-to-scheduled-executor.yaml

@@ -19,7 +19,7 @@ oldCode: |-
   }, 0, 60_000);
 modernCode: |-
   ScheduledExecutorService scheduler =
-          Executors.newSingleThreadScheduledExecutor();
+          Executors.newScheduledThreadPool(2);
 
   scheduler.scheduleAtFixedRate(
           this::refresh, 0, 1, TimeUnit.MINUTES);

proof/concurrency/TimerTaskToScheduledExecutor.java

@@ -8,7 +8,7 @@ void main() throws Exception {
     Runnable refresh = () -> System.out.println("refresh");
 
     ScheduledExecutorService scheduler =
-            Executors.newSingleThreadScheduledExecutor();
+            Executors.newScheduledThreadPool(2);
 
     ScheduledFuture<?> future = scheduler.scheduleAtFixedRate(
             refresh, 0, 1, TimeUnit.MINUTES);