Bump to Go 1.18 (with support for the new any keyword)

[applejag]

Describe the PR
These are @rdlaitila's changes to make swaggo work with Go 1.18. Their changes are 2 weeks old, and so I thought to push @rdlaitila's changes and put effort in adjusting it for any review comments.

Relation issue
Closes #1162

Additional context
I do not know who @rdlaitila is, I just found their changes mentioned in the related issue.

[codecov]

Codecov Report

Merging #1168 (06c66d5) into master (2b64f78) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 06c66d5 differs from pull request most recent head 6269dae. Consider uploading reports for the commit 6269dae to get more accurate results

@@           Coverage Diff           @@
##           master    #1168   +/-   ##
=======================================
  Coverage   94.76%   94.77%           
=======================================
  Files          10       10           
  Lines        2447     2449    +2     
=======================================
+ Hits         2319     2321    +2     
  Misses         67       67           
  Partials       61       61           

Impacted Files	Coverage Δ
operation.go	96.01% <100.00%> (+0.01%)	⬆️
schema.go	100.00% <100.00%> (ø)

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[ubogdan]

LGTM

[ubogdan]

@jilleJr Thanks for your contribution.