Managing Go Modules

---
name: managing-go-modules
description: |
  Use when working with Go Modules — go modules package management. Covers
  module initialization, dependency resolution, version management, module
  proxying, vendoring, and vulnerability scanning. Use when managing Go modules,
  resolving dependency conflicts, analyzing module graphs, or auditing module
  vulnerabilities.
connection_type: go-modules
preload: false
---

# Go Modules Management Skill

Manage and analyze Go module dependencies, versions, and vulnerability scanning.

## MANDATORY: Discovery-First Pattern

**Always check current go.mod configuration before modifying dependencies.**

### Phase 1: Discovery

```bash
#!/bin/bash

echo "=== Module Info ==="
head -5 go.mod 2>/dev/null

echo ""
echo "=== Go Version ==="
go version 2>/dev/null

echo ""
echo "=== Direct Dependencies ==="
grep -v '// indirect' go.mod 2>/dev/null | grep -E '^\t' | head -15

echo ""
echo "=== Go Environment ==="
go env GOPATH GOMODCACHE GOPROXY GONOSUMCHECK 2>/dev/null
```

### Phase 2: Analysis

```bash
#!/bin/bash

echo "=== Module Graph Summary ==="
go mod graph 2>/dev/null | wc -l | xargs -I{} echo "Total dependency edges: {}"

echo ""
echo "=== Outdated Modules ==="
go list -u -m all 2>/dev/null | grep '\[' | head -15

echo ""
echo "=== Vulnerability Scan ==="
go install golang.org/x/vuln/cmd/govulncheck@latest 2>/dev/null
govulncheck ./... 2>/dev/null | head -20
```

## Output Rules
- **TOKEN EFFICIENCY**: Target <=50 lines per output
- List direct vs indirect dependencies separately
- Report vulnerability findings concisely
- Show module graph density, not full graph

## Common Operations

### Module Tidying

```bash
#!/bin/bash
echo "=== Tidy Check ==="
cp go.mod go.mod.bak
go mod tidy 2>&1
diff go.mod.bak go.mod 2>/dev/null | head -15
rm go.mod.bak 2>/dev/null
```

### Module Lookup

```bash
#!/bin/bash
MODULE="${1:?Module path required}"
echo "=== Module Info: $MODULE ==="
go list -m -json "$MODULE@latest" 2>/dev/null | jq '{
  Path: .Path,
  Version: .Version,
  Time: .Time
}' 2>/dev/null

echo ""
echo "=== Available Versions ==="
go list -m -versions "$MODULE" 2>/dev/null
```

## Safety Rules

- **Run `go mod tidy`** after adding or removing dependencies
- **Review go.sum changes** before committing -- unexpected changes may indicate supply chain issues
- **Use `govulncheck`** before releases to scan for known vulnerabilities
- **Vendor dependencies** for critical production services with `go mod vendor`

## Output Format

Present results as a structured report:
```
Managing Go Modules Report
══════════════════════════
Resources discovered: [count]

Resource       Status    Key Metric    Issues
──────────────────────────────────────────────
[name]         [ok/warn] [value]       [findings]

Summary: [total] resources | [ok] healthy | [warn] warnings | [crit] critical
Action Items: [list of prioritized findings]
```

Target ≤50 lines of output. Use tables for multi-resource comparisons.

## Anti-Hallucination Rules

1. **NEVER assume resource names** — always discover via CLI/API in Phase 1 before referencing in Phase 2.
2. **NEVER fabricate metric names or dimensions** — verify against the service documentation or `--help` output.
3. **NEVER mix CLI commands between service versions** — confirm which version/API you are targeting.
4. **ALWAYS use the discovery → verify → analyze chain** — every resource referenced must have been discovered first.
5. **ALWAYS handle empty results gracefully** — an empty response is valid data, not an error to retry.

## Counter-Rationalizations

| Shortcut | Counter | Why |
|----------|---------|-----|
| "I'll skip discovery and check known resources" | Always run Phase 1 discovery first | Resource names change, new resources appear — assumed names cause errors |
| "The user only asked for a quick check" | Follow the full discovery → analysis flow | Quick checks miss critical issues; structured analysis catches silent failures |
| "Default configuration is probably fine" | Audit configuration explicitly | Defaults often leave logging, security, and optimization features disabled |
| "Metrics aren't needed for this" | Always check relevant metrics when available | API/CLI responses show current state; metrics reveal trends and intermittent issues |
| "I don't have access to that" | Try the command and report the actual error | Assumed permission failures prevent useful investigation; actual errors are informative |