[time-duration] Implement time-duration concept and time-keeper concept exercise

Programming Go
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1

I created the PR #3126 to solve the ticket Implement new Concept Exercise: time-duration, including:

  • Add new concept time-duration
  • Implement new concept exercise time-keeper
2

Thank you for the PR. In the future, please discuss changes on the forum before doing any work. Many repos and/or issues are not accepting community contributions and unsolicited PRs are not considered!

I’ll have a look at this PR.