Upgrade all references to go1.18 and replace go get with go install

[moshebe]

• go1.17 -> go1.18
• go get x -> go install x@latest

[codecov-commenter]

Codecov Report

Merging #474 (b791659) into master (4d7037f) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #474   +/-   ##
=======================================
  Coverage   78.27%   78.27%           
=======================================
  Files           7        7           
  Lines         290      290           
=======================================
  Hits          227      227           
  Misses         39       39           
  Partials       24       24           

Impacted Files	Coverage Δ
pkg/config/render.go	93.93% <100.00%> (ø)

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