Update go version to 1.18.6

[khewonc]

What does this PR do?

Avoid GHSA-69cg-p879-7622

Motivation

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Additional Notes

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Describe your test plan

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[codecov-commenter]

Codecov Report

Merging #151 (715633f) into main (8ed9884) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #151   +/-   ##
=======================================
  Coverage   63.22%   63.22%           
=======================================
  Files          41       41           
  Lines        3073     3073           
=======================================
  Hits         1943     1943           
  Misses       1014     1014           
  Partials      116      116           

Flag	Coverage Δ
unittests	63.22% <ø> (ø)

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