os/gcron: unit testing case of package gcron occasionally failed

[gqcn]

Description

https://github.com/gogf/gf/actions/runs/12106520144/job/33752355822?pr=3997

The unit testing case codes are here:

Additional

The cron job is not always precise as we expect, so we should consider it when we write the unit testing case.

[github-actions]

Hello @gqcn. We like your proposal/feedback and would appreciate a contribution via a Pull Request by you or another community member. We thank you in advance for your contribution and are looking forward to reviewing it!
你好 @gqcn。我们喜欢您的提案/反馈，并希望您或其他社区成员通过拉取请求做出贡献。我们提前感谢您的贡献，并期待对其进行审查。