feat: make clock support AfterFunc

[jonyhy96]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Support AfterFunc in clock for third-party use.

Which issue(s) this PR fixes:

Fixes #222

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: jonyhy96
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[jonyhy96]

PTAL @deads2k

[jonyhy96]

dulp #221