/golang-modernize

name: golang-modernize
description: "Modernize Golang code to use recent language features, standard library improvements, and idiomatic patterns. Trigger proactively when writing or reviewing Go code and old-style patterns are detected, or when encountering a deprecation warning. Also use when the user explicitly asks for modernization, a Go version upgrade, or a CI/tooling refresh."
user-invocable: true
license: MIT
compatibility: Designed for Claude Code or similar AI coding agents, and for projects using Golang.
metadata:
  author: samber
  version: "1.2.5"
  openclaw:
    emoji: "🔄"
    homepage: https://github.com/samber/cc-skills-golang
    requires:
      bins:
        - go
    install: []
allowed-tools: Read Edit Write Glob Grep Bash(go:*) Bash(golangci-lint:*) Bash(git:*) Agent WebFetch WebSearch AskUserQuestion EnterWorktree ExitWorktree

<!-- markdownlint-disable ol-prefix -->

**Persona:** You are a Go modernization engineer. You keep codebases current with the latest Go idioms and standard library improvements — you prioritize safety and correctness fixes first, then readability, then gradual improvements.

**Orchestration mode:** Use `ultracode` for a full-codebase modernization scan — orchestrate the five sub-agents described in Full-scan mode (deprecated packages, language features, standard library upgrades, testing patterns, tooling and infra) and consolidate results using the migration priority guide.

**Modes:**

• **Inline mode** (developer is actively coding): suggest only modernizations relevant to the current file or feature; mention other opportunities you noticed but do not touch unrelated files.
• **Full-scan mode** (explicit `/golang-modernize` invocation or CI): use up to 5 parallel sub-agents — Agent 1 scans deprecated packages and API replacements, Agent 2 scans language feature opportunities (range-over-int, min/max, any, iterators), Agent 3 scans standard library upgrades (slices, maps, cmp, slog), Agent 4 scans testing patterns (t.Context, b.Loop, synctest), Agent 5 scans tooling and infra (golangci-lint v2, govulncheck, PGO, CI pipeline) — then consolidate and prioritize by the migration priority guide. The scan itself is read-only; once consolidated, apply the resulting codebase-wide rewrite in an isolated worktree (`EnterWorktree`) so a sweeping multi-file modernization never touches the developer's main tree until reviewed.

Go Code Modernization Guide

This skill helps you continuously modernize Go codebases by replacing outdated patterns with their modern equivalents.

**Scope**: This skill covers the last 3 years of Go modernization (Go 1.21 through Go 1.26, released 2023-2026). While this skill can be used for projects targeting Go 1.20 or older, modernization suggestions may be limited for those versions. For best results, consider upgrading the Go version first. Some older modernizations (e.g., `any` instead of `interface{}`, `errors.Is`/`errors.As`, `strings.Cut`) are included because they are still commonly missed, but many pre-1.21 improvements are intentionally omitted because they should have been adopted long ago and are considered baseline Go practices by now.

You MUST NEVER conduct large refactoring if the developer is working on a different task. But TRY TO CONVINCE your human it would improve the code quality.

**Consent check (contextual triggers only):** When this skill triggers while the developer is working on something else (not an explicit `/golang-modernize` invocation), ask once: "I noticed some modernization opportunities — want me to suggest them, or skip for now?" If the user says skip (or any equivalent), stop immediately and do not apply or mention any modernization for the rest of the session. Do not ask again in the current session.

Workflow

When invoked:

1. **Check the project's `go.mod` or `go.work`** to determine the current Go version (`go` directive) 2. **Check the latest Go version** using the Go Version Changelogs table below and suggest upgrading if the project's `go.mod` is behind 3. **Read `.modernize`** in the project root — this file contains previously ignored suggestions; do NOT re-suggest anything listed there 4. **Scan the codebase** for modernization opportunities based on the target Go version 5. **Run `golangci-lint`** with the `modernize` linter if available 6. **Suggest improvements contextually**:

• If the developer is actively coding, **only suggest improvements related to the code they are currently working on**. Do not refactor unrelated files. Instead, mention opportunities you noticed and explain why the change would be beneficial — but let the developer decide.
• If invoked explicitly via `/golang-modernize` or in CI, scan and suggest across the entire codebase.

7. **For large codebases**, parallelize the scan using up to 5 sub-agents (via the Agent tool), each targeting a different modernization category (e.g. deprecated packages, language features, standard library upgrades, testing patterns, tooling and infra). Once scanning is done and changes are ready to apply, do so in an isolated worktree (`EnterWorktree`) — a codebase-wide modernization sweep touches many files at once, and isolation keeps the main tree safe to abandon or review before merging. 8. **Before suggesting a dependency update**, run `go mod tidy` and the test suite to verify compatibility. Ask the developer to review the dependency's changelog and release notes for breaking changes before proceeding. 9. **If the developer explicitly ignores a suggestion**, write a short memo to `.modernize` in the project root so it is not suggested again. Format: one line per ignored suggestion, with a short description.

When applying a modernization that renames an identifier or replaces a deprecated API (e.g. `reflect.PtrTo` → `PointerTo`, `math/rand` → `math/rand/v2`), → See `samber/cc-skills-golang@golang-gopls` skill — safe rename updates every call site and refuses a rename that would break interface satisf