ci: re-enacted linting

[fredbi]

• re-enacted golangci-lint run in github action
• re-enacted codecov uploads in github action

[codecov[bot]]

Codecov Report

Attention: 16 lines in your changes are missing coverage. Please review.

Comparison is base (e8e27ff) 62.92% compared to head (d8ccc36) 63.37%. Report is 18 commits behind head on master.

Files	Patch %	Lines
info.go	33.33%	6 Missing and 2 partials :warning:
responses.go	58.82%	5 Missing and 2 partials :warning:
properties.go	66.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #169 +/- ## ========================================== + Coverage 62.92% 63.37% +0.45% ========================================== Files 28 30 +2 Lines 2058 3072 +1014 ========================================== + Hits 1295 1947 +652 - Misses 593 951 +358 - Partials 170 174 +4 ``` | [Flag](https://app.codecov.io/gh/go-openapi/spec/pull/169/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi) | Coverage Δ | | |---|---|---| | [oldstable](https://app.codecov.io/gh/go-openapi/spec/pull/169/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi) | `63.37% <65.95%> (?)` | | | [stable](https://app.codecov.io/gh/go-openapi/spec/pull/169/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi) | `63.37% <65.95%> (?)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=go-openapi#carryforward-flags-in-the-pull-request-comment) to find out more.

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