chore: add go mod support

[mboersma]

Reason for Change:
Adds go module support for dependency vendoring, but doesn't remove dep stuff yet.

All credit goes to @andyliuliming, I just polished this up.

Issue Fixed:
Replaces #1077

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:
@andyliuliming is this important for AKS vendoring, or just something to future-proof us?

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[codecov]

Codecov Report

Merging #1435 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1435   +/-   ##
=======================================
  Coverage   75.56%   75.56%           
=======================================
  Files         128      128           
  Lines       18039    18039           
=======================================
  Hits        13632    13632           
  Misses       3618     3618           
  Partials      789      789

[mboersma]

There's no particular urgency to this, so let's put it on the back burner again until there is an actual need. I'll keep the branch around.