golang-modernize

golang-modernize is a skill for Claude Code from alexastrum/skl. It costs 70 tokens per session (2,620 once invoked), scanned A, original, MIT.

A guide to updating Go code to current language features, standard-library APIs, testing practices, and development tools. It applies these improvements either while editing code or across a requested full scan.

In plain words
What is it for?
Use it when writing, reviewing, or upgrading Go code, especially after a Go version change or a deprecation warning. It can check language features, standard-library packages, tests, linters, vulnerability checks, profiling, and CI.
Why use it?
It helps find outdated code, deprecated APIs, and newer patterns that can improve safety, readability, and maintenance. It also organizes modernization work by priority instead of changing everything at once.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions subagents; names the AskUserQuestion tool; mentions Claude Code.

Good fit Use it when writing, reviewing, or upgrading Go code, especially after a Go version change or a deprecation warning. It can check language features, standard-library packages, tests, linters, vulnerability checks, profiling, and CI.

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Install with agentmods
npx agentmods add skills/alexastrum/skl/golang-modernize
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add alexastrum/skl --skill golang-modernize
Clone the repo
git clone --depth 1 https://github.com/alexastrum/skl

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for golang-modernize

README.md
[![agentmods](https://agentmods.dev/badge/skills/alexastrum/skl/golang-modernize/github.svg)](https://agentmods.dev/skills/alexastrum/skl/golang-modernize)
Your own site
<a href="https://agentmods.dev/skills/alexastrum/skl/golang-modernize"><img src="https://agentmods.dev/badge/skills/alexastrum/skl/golang-modernize/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for golang-modernize

Your own site · 80×15
<a href="https://agentmods.dev/skills/alexastrum/skl/golang-modernize"><img src="https://agentmods.dev/badge/skills/alexastrum/skl/golang-modernize.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 70 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,620 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00070 $0.02620
Opus 5 $0.00035 $0.01310
Sonnet 5 $0.00014 $0.00524
Haiku 4.5 $0.00007 $0.00262

Measured 11d ago against content hash baf5ecd8180e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

golang-modernize scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/golang-modernize/SKILL.md · 153 lines

How it starts

The opening of the file, as written. The whole thing — 153 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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.

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.

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.

Read the full file on GitHub · 153 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 153 lines · 70 tokens per session scan A baf5ecd8180e

Subscribe to this mod's changes

golang-modernize is a skill published in the GitHub repository alexastrum/skl (11 stars, last pushed 3mo ago), licensed MIT. It adds 70 tokens to every session and 2,620 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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