Update go to 1.12.5

[alessio]

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.
• Wrote tests
• Updated relevant documentation (docs/)
• Added a relevant changelog entry: clog add [section] [stanza] [message]
• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[alexanderbez]

Beat me to it. ACK

[codecov]

Codecov Report

Merging #4343 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4343      +/-   ##
==========================================
- Coverage   59.38%   59.37%   -0.02%     
==========================================
  Files         214      214              
  Lines       14533    14533              
==========================================
- Hits         8631     8629       -2     
- Misses       5264     5266       +2     
  Partials      638      638