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Go Precommit Checks

make precommit runs these checks. Know the rules BEFORE writing code to avoid iteration loops.

Complexity Limits (golangci-lint)

funlen:    80 lines max per function    # split into helper functions
gocognit:  20 complexity max            # reduce nesting, early returns
nestif:    4 nesting levels max         # extract conditions into methods
maintidx:  20 maintainability min       # keep functions focused

How to stay under limits:

  • Extract helper functions at 40+ lines (leave room for growth)
  • Use early returns instead of nested if/else
  • Extract complex conditions: if s.isReady(ctx) not if s.x && s.y || s.z
  • One concern per function

Line Length

golines enforces max 100 characters. Write short lines from the start:

// ❌ BAD: will be reformatted
result, err := s.longServiceName.DoSomethingComplex(ctx, param1, param2, param3)

// ✅ GOOD: already within limit
result, err := s.svc.DoSomething(
    ctx, param1, param2, param3,
)

Banned Packages (depguard)

// ❌ BANNED                          // ✅ USE INSTEAD
"github.com/pkg/errors"              // github.com/bborbe/errors
"github.com/bborbe/argument"         // github.com/bborbe/argument/v2
"golang.org/x/net/context"           // context (stdlib)
"golang.org/x/lint/golint"           // revive or staticcheck
"io/ioutil"                          // io and os packages

Error Checking (errcheck)

Every error must be checked. Exceptions: Close, Write, Fprint.

// ❌ BAD: errcheck will fail
os.Remove(path)
os.Chmod(path, 0600)

// ✅ GOOD
_ = os.Remove(path)  // cleanup, error irrelevant
if err := os.Chmod(path, 0600); err != nil {
    return errors.Wrap(ctx, err, "chmod")
}

License Headers (addlicense)

Every .go file needs BSD header. Auto-added by make precommit but write it yourself on new files:

// Copyright (c) 2026 Benjamin Borbe All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

Mock Generation

make precommit deletes and regenerates mocks/. Never hand-write mocks.

Checklist (before running make precommit)

  • Functions under 80 lines
  • Nesting under 4 levels
  • Lines under 100 chars
  • No banned packages
  • All errors checked
  • License header on new files
  • #nosec annotations have reasons (see go-security-linting.md)
  • Use slices.Contains instead of manual loops — slicescontains linter enforces this