ci: run go fix as part of the lint workflow

[marten-seemann]

Run go fix -diff as part of the lint workflow

• Adds a new step in lint.yml that runs go fix -diff ./... for Go 1.25.x, surfacing any fixes suggested by the current Go toolchain.
• Updates qpack_test.go to apply go fix changes to the replaceRandomCharacter helper, replacing intermediate variable usage with direct slice concatenation.
• The golangci-lint step is updated with if: success() || failure() so it still runs even when the go fix step fails.

^{Macroscope summarized 05f5846.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.55%. Comparing base (77b3bdb) to head (05f5846).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #90   +/-   ##
=======================================
  Coverage   93.55%   93.55%           
=======================================
  Files           4        4           
  Lines         186      186           
=======================================
  Hits          174      174           
  Misses          6        6           
  Partials        6        6           

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[Copilot]

Pull request overview

This PR updates the lint CI workflow to run go fix -diff ./... (on Go 1.25.x) and applies the corresponding go fix rewrite to a helper in qpack_test.go.

Changes:

• Add a go fix -diff ./... step to the lint workflow for Go 1.25.x.
• Update replaceRandomCharacter in qpack_test.go per go fix output.
• Adjust lint workflow step conditions so golangci-lint can run even if go fix fails.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
qpack_test.go	Applies go fix-driven simplification to the replaceRandomCharacter test helper.
.github/workflows/lint.yml	Adds a go fix -diff step and updates conditional execution for lint steps.

Comments suppressed due to low confidence (1)

.github/workflows/lint.yml:28

• The step-level if: success() || failure() conditions are broader than intended: they make go fix/golangci-lint run even if actions/setup-go fails, which can create misleading secondary errors (e.g., go: command not found) and obscure the root cause. Consider (1) letting go fix run only when Go setup succeeded, and (2) running golangci-lint with always() but gated on setup-go success so it still runs when go fix fails (the stated goal) without running after a failed toolchain setup.

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[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks

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_{Comparing go-fix (05f5846) with master (77b3bdb)}