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.
npx skills add cxuu/golang-skills --skill go-defensivegit clone --depth 1 https://github.com/cxuu/golang-skillsWrote 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.
[](https://agentmods.dev/skills/cxuu/golang-skills/go-defensive)<a href="https://agentmods.dev/skills/cxuu/golang-skills/go-defensive"><img src="https://agentmods.dev/badge/skills/cxuu/golang-skills/go-defensive/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.
<a href="https://agentmods.dev/skills/cxuu/golang-skills/go-defensive"><img src="https://agentmods.dev/badge/skills/cxuu/golang-skills/go-defensive.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00076 | $0.01596 |
| Opus 5 | $0.00038 | $0.00798 |
| Sonnet 5 | $0.00015 | $0.00319 |
| Haiku 4.5 | $0.00008 | $0.00160 |
Grade A, and why
go-defensive 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 12d 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.
How it starts
The opening of the file, as written. The whole thing — 193 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Go Defensive Programming Patterns
Compatibility: Crypto examples may use
crypto/rand.Text, which requires Go 1.24+.
Resource Routing
references/BOUNDARY-COPYING.md- Read when copying slices/maps across API boundaries.references/GLOBAL-STATE.md- Read when introducing or removing package globals.references/MUST-FUNCTIONS.md- Read when deciding whether a panic-on-error helper is acceptable.references/PANIC-RECOVER.md- Read when evaluating panic, recover, or crash containment.references/TIME-ENUMS-TAGS.md- Read when handling time types, enum zero values, or struct tags.
Defensive Checklist Priority
When hardening code at API boundaries, check in this order:
Reviewing an API boundary?
├─ 1. Error handling → Return errors; don't panic (see go-error-handling)
├─ 2. Input validation → Copy slices/maps received from callers
├─ 3. Output safety → Copy slices/maps before returning to callers
├─ 4. Resource cleanup → Use defer for Close/Unlock/Cancel
├─ 5. Interface checks → Route compile-time assertions to go-interfaces
├─ 6. Time correctness → Use time.Time and time.Duration, not int/float
├─ 7. Enum safety → Start iota at 1 so zero-value is invalid
└─ 8. Crypto safety → crypto/rand for keys, never math/rand
Quick Reference
| Pattern | Rule | Details |
|---|---|---|
| Boundary copies | Copy slices/maps on receive and return | BOUNDARY-COPYING.md |
| Defer cleanup | defer f.Close() right after os.Open |
Below |
| Interface check | Compile-time satisfaction assertion | See go-interfaces |
| Time types | time.Time / time.Duration, never raw int |
TIME-ENUMS-TAGS.md |
| Enum start | iota + 1 so zero = invalid |
Below |
| Crypto rand | crypto/rand for keys, never math/rand |
Below |
| Must functions | Only at init; panic on failure | MUST-FUNCTIONS.md |
| Panic/recover | Never expose panics across packages | PANIC-RECOVER.md |
| Mutable globals | Replace with dependency injection | Below |
What ships with it
5 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.
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.
- 12d ago First seen · 193 lines · 76 tokens per session scan A ae5a2a22f763
go-defensive is a skill published in the GitHub repository cxuu/golang-skills (159 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 76 tokens to every session and 1,596 once invoked, about $0.0004 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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