chore(jest-runner): Add info regarding timers to forceExited message (#12083)

Author: silverwind

CHANGELOG.md

@@ -17,6 +17,7 @@
 
 ### Chore & Maintenance
 
+- `[jest-runner]` Add info regarding timers to forcedExit message([#12083](https://github.com/facebook/jest/pull/12083))
 - `[*]` Replaced `substr` method with `substring` ([#12066](https://github.com/facebook/jest/pull/12066))
 
 ### Performance

packages/jest-runner/src/index.ts

@@ -273,7 +273,8 @@ export default class TestRunner {
           chalk.yellow(
             'A worker process has failed to exit gracefully and has been force exited. ' +
               'This is likely caused by tests leaking due to improper teardown. ' +
-              'Try running with --detectOpenHandles to find leaks.',
+              'Try running with --detectOpenHandles to find leaks. ' +
+              'Active timers can also cause this, ensure that .unref() was called on them.',
           ),
         );
       }