ci: bump to go 1.18

[mmcloughlin]

No description provided.

[codecov-commenter]

Codecov Report

Merging #239 (fb751d2) into master (72b8db9) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #239   +/-   ##
=======================================
  Coverage   76.12%   76.12%           
=======================================
  Files          65       65           
  Lines       20538    20538           
=======================================
  Hits        15634    15634           
  Misses       4825     4825           
  Partials       79       79           

Flag	Coverage Δ
integration	11.84% <ø> (ø)
stress	?
unittests	73.22% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 72b8db9...fb751d2. Read the comment docs.

[mmcloughlin]

Lint errors due to the deprecation of go/types APIs. See discussions:

https://gophers.slack.com/archives/C0VP8EF3R/p1648446308143889
https://gophers.slack.com/archives/CBL6Z5U7J/p1648447277176839

dominikh/go-tools@b798260 will address this, but hasn't landed in a staticcheck release yet. That should be coming in a day or so, hopefully the inclusion in golangci-lint would be soon after.