fix: Prevent goroutine leak in Crontab by adding graceful shutdown support

[tharunn0]

Description:

Updates the crontab background job runner to support graceful shutdown, replacing the infinite for ... range ticker loop with a select statement that listens for a termination signal.
Previously, terminating the application would inadvertently leak the associated background goroutine because it lacked an explicit exit condition.
The changes align the crontab implementation with the framework's graceful shutdown lifecycle by integrating the new Crontab.Stop() method into App.Shutdown.

Fixes goroutine leak during crontab shutdown

Breaking Changes (if applicable):

• None

Additional Information:

• None

Checklist:

• I have formatted my code using goimport and golangci-lint.
• All new code is covered by unit tests.
• This PR does not decrease the overall code coverage.
• I have reviewed the code comments and documentation for clarity.

Fixes #3211

[Umang01-hash]

@tharunn0 Thanks for the effort to make GoFr better. Here are a few things that should be fixed before we go ahead with the PR:

Issue 1 : Double-Stop panics

close(c.done) will panic if Stop() is called twice. While ticker.Stop() is idempotent, close() on an already-closed channel is not. Use sync.Once:

type Crontab struct {
    // ...
    done     chan struct{}
    stopOnce sync.Once
}

func (c *Crontab) Stop() {
    c.stopOnce.Do(func() {
        c.ticker.Stop()
        close(c.done)
    })
}

Issue 2 Shutdown ordering

cron.Stop() is placed after a.container.Close() in Shutdown(). This means datasources are closed before cron scheduling stops — a cron job could fire against closed datasources in that window. Move cron stop before container close:

if a.cron != nil {
    a.cron.Stop()
}

if a.container != nil {
    err = errors.Join(err, a.container.Close())
}

Issue 3 : Missing integration test

TestCrontab_Stop only tests standalone Stop(). Consider adding a test that verifies App.Shutdown() properly stops cron — e.g., create an App, add a cron job, call Shutdown, assert the goroutine exits.