update golang version to 1.18.6

[celenechang]

What does this PR do?

Address GHSA-69cg-p879-7622

Motivation

What inspired you to submit this pull request?

Additional Notes

Anything else we should know when reviewing?

Describe your test plan

Make sure this log line is observed on startup:
{"level":"INFO","ts":"2022-09-14T02:21:11Z","logger":"setup","msg":"Go Version: go1.18.6"}

[codecov-commenter]

Codecov Report

Merging #612 (ac4535c) into main (a05d2cb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #612   +/-   ##
=======================================
  Coverage   58.51%   58.51%           
=======================================
  Files           3        3           
  Lines         135      135           
=======================================
  Hits           79       79           
  Misses         43       43           
  Partials       13       13           

Flag	Coverage Δ
unittests	58.51% <ø> (ø)

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