lint: replace deprecated golang.org/x/lint/golint with golangci-lint

[pohly]

golint is deprecated. golangci-lint is a more than adequate replacement. Because it combines different linters, a single invocation in the Makefile is enough and then produces consistent output for all of them.

It also gets enabled as a GitHub action. This will annotate pull requests.

The godox linter gets enabled as replacement for the manual "grep -i fixme".

For the sake of convenience, "make lint" installs golangci-lint. In contrast to golint before, this is done without polluting the go.mod file with the extra dependencies.

Fixes: #92

[codecov]

Codecov Report

Merging #95 (a7c49f9) into master (70e025e) will not change coverage.
The diff coverage is n/a.

❗ Current head a7c49f9 differs from pull request most recent head 2b5723b. Consider uploading reports for the commit 2b5723b to get more accurate results

@@           Coverage Diff           @@
##           master      #95   +/-   ##
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  Coverage   94.92%   94.92%           
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  Files           5        5           
  Lines         138      138           
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  Hits          131      131           
  Misses          4        4           
  Partials        3        3           

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[CLAassistant]

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[liggitt]

should the gofmt / go vet / fixme checks remain?

[pohly]

"govet" is enabled by default in golangci-lint. I explicitly enabled "godox" as replacement for the grep command.

What I got wrong is "gofmt": I thought it was enabled by default., but it isn't. Will fix....

... and of course it helps to actually include the .golangci.yml in the commit 🥵

[pohly]

@prashantv: do you want me to rebase or shall I close this PR? Entirely up to you, I'm fine with both.

[prashantv]

@pohly Thanks for the PR, since revive is a drop-in replacement that runs faster, I put that up in #97.

I think let's keep both open to see what direction others prefer -- if golangci-lint is preferred, then this PR can be rebased.

[abhinav]

Thanks, @pohly.
This can probably be closed now that #97 is merged.
(golangci-lint is cool, but it does a lot more than golint. If we ever switch to it, we'll want to drop staticcheck as well since golangci-lint bundles it in too.)

[pohly]

Please don't forget to do a release 😄