upgrade go version 1.12.9 -> 1.12.12

[tanjunchen]

There is a CVE for Go and this vulnerability is fixed in 1.12.12. We should update it.
See: https://nvd.nist.gov/vuln/detail/CVE-2019-16276

See issue golang/go#34540
Seems this is fixed in 1.12.12. I suggest we should update to 1.12.12 first

/kind bug
/priority important-soon

Fixes#5675

[k8s-ci-robot]

Hi @tanjunchen. Thanks for your PR.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: tanjunchen
To complete the pull request process, please assign afbjorklund
You can assign the PR to them by writing /assign @afbjorklund in a comment when ready.

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[minikube-bot]

Can one of the admins verify this patch?

[tanjunchen]

/assign @afbjorklund

[codecov-io]

Codecov Report

Merging #5676 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #5676   +/-   ##
======================================
  Coverage    37.7%   37.7%           
======================================
  Files         103     103           
  Lines        7617    7617           
======================================
  Hits         2872    2872           
  Misses       4368    4368           
  Partials      377     377

[afbjorklund]

Sounds good

/ok-to-test