Fix linting

[WillAbides]

I noticed that .golangci.yml had some commented out and disabled linters. This PR fixes that. It also uncomments "example" from the GitHub action.

Running go mod tidy -compat 1.17 fixed the "no go files to analyze" error linting "examples".¹

For the linting issues, I updated .golangci-lint and fixed the issues that it found.

I think most of the changes are obvious, but I want to mention a few things:

• I created two test helpers "assertNilError" and "assertWrite" because that made the error checks issues easier to fix with find/replace. I see that assert functions are generally not used in this repo. I'm happy to inline these, but my preference is to keep them as-is.
• I changed the signature of stringifyValue to accept a *bytes.Buffer instead of an io.Writer because the linter knows that Buffer.Write always returns nil errors.
• I removed quite a bit of dead code from authorizations_test.go

Footnotes

1. examples/go.* changes were originally part of this PR, but merging Remove dependency on "golang.org/x/oauth2" #2895 removed them from the diff. ↩

[codecov]

Codecov Report

Merging #2903 (1f47817) into master (66b1147) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@ Coverage Diff @@## master #2903 +/- ##
==========================================
+ Coverage 98.14% 98.17% +0.03% 
==========================================
Files 143 143 Lines 12606 12609 +3 ==========================================
+ Hits 12372 12379 +7 + Misses 159 156 -3 + Partials 75 74 -1 

Files Changed	Coverage Δ
github/actions_secrets.go	100.00% <100.00%> (ø)
github/github.go	98.11% <100.00%> (+<0.01%)	⬆️
github/repos_releases.go	91.13% <100.00%> (+1.68%)	⬆️
github/strings.go	100.00% <100.00%> (ø)

📢 Have feedback on the report? Share it here.

[WillAbides]

Codecov didn't like that I modified an uncovered line, so I added a test for it.

[gmlewis]

I'm doing a crazy amount of driving today, so will be slow to respond. I try to "approve run" of the checks when I can, but today's going to be pretty challenging, sorry.

[WillAbides]

@gmlewis I appreciate how responsive you are on this repo. I have no expectation that you or anybody else be around on a weekend. I can see the lint results on my fork, so my feedback loop is just fine.

[gmlewis]

Wow, @WillAbides - thank you for this huge cleanup! It is greatly appreciated!
LGTM.

Awaiting second LGTM+Approval from any other contributor to this repo before merging.

[gabriel-samfira]

This is awesome

[gmlewis]

Thank you, @gabriel-samfira !
Merging.