go-guidelines-marketplace

Go Guidelines for Code Agents

A plugin that teaches AI code agents how to write production-grade Go — covering modern syntax, generics, performance, concurrency safety, error handling, testing, and best practices.

Drop it into Cursor or Claude Code and every Go file the agent touches gets better.

Motivation

All coding agents tend to generate outdated and suboptimal Go. Key reasons:

1. Training data lag. Models don't know about features added after their training cutoff. They can't use wg.Go() (1.25), new(val) (1.26), or errors.AsType[T] (1.26) if they've never seen them.

2. Frequency bias. Even for features the model knows, it picks older patterns. There's more for i := 0; i < n; i++ in the training data than for i := range n, so that's what comes out.

3. No performance awareness. Agents don't align struct fields, don't set GOMAXPROCS for containers, and spawn unbounded goroutines instead of using pools.

4. Broken operational patterns. Generated shutdown code closes the database before draining the HTTP server. Resources get leaked. Signals get ignored.

5. No post-change verification. Agents never run golangci-lint or tests with the race detector after making changes.

These guidelines fix all of the above by giving the agent an explicit, version-aware reference. The agent detects your Go version from go.mod and applies only the features and patterns available up to that version.

This aligns with the Go team's direction. The modernize analyzer exists to update existing code to use newer idioms. These guidelines serve the same goal for new code: agents write modern Go from the start, so there's less to fix later.

What the Agent Learns

Modern Syntax	Version-aware features from Go 1.0 through 1.26 — the agent detects your go.mod version and stays within bounds
Performance	Struct alignment, sync.Pool, pre-allocation, buffered channels, pointer semantics, strings.Builder, escape analysis
Patterns	Naming conventions, context-first parameters, functional options, graceful shutdown, health checks, consumer-side interfaces, guard clauses, defer pitfalls, HTTP client best practices, io.Reader, resource closing
Concurrency	Goroutine leak prevention, bounded concurrency with errgroup, channel safety, select randomness, nil channels, notification channels, mutex pitfalls, false sharing
Testing	Table-driven tests, t.Helper/t.Cleanup, httptest, race detector, mockery, goleak, fuzz testing, synctest, benchmark pitfalls, test categorization
Error Handling	Error types decision matrix, %w wrapping, naming conventions, handle-once principle, panic/recover
Generics	Type parameters, constraints, comparable, common mistakes, when to use/avoid, version-specific features
Pitfalls	Nil interface trap, variable shadowing, nil map panic, break in switch/select, copying sync types, time.After leak, init misuse, type embedding, trim confusion, string formatting deadlocks
Slices & Maps	Backing array retention, append aliasing, 3-index slice, pointer-in-slice leak, maps never shrink, map pointer instability, nil slice behavior
Context	Type-safe keys, WithoutCancel, AfterFunc, WithCancelCause, request-scoped propagation, timeout layering
Post-Change	Automatically runs golangci-lint (or go vet fallback) and go test -race on changed packages

File Structure

claude/go-guidelines/skills/go-guidelines/
├── SKILL.md                          # Entry point — version detection + reference routing
└── references/
    ├── modern-syntax.md              # Go version-specific syntax (1.0 → 1.26)
    ├── performance.md                # Struct layout, pre-allocation, sync.Pool, escape analysis
    ├── concurrency.md                # errgroup, goroutine leaks, select, false sharing
    ├── patterns.md                   # Naming, interfaces, shutdown, health checks, io.Reader
    ├── testing.md                    # Table tests, httptest, goleak, fuzz, benchmarks
    ├── error-handling.md             # Error types, wrapping, panic/recover
    ├── generics.md                   # Type parameters, constraints, common mistakes
    ├── pitfalls.md                   # Nil traps, shadowing, sync copy, init, time, defer
    ├── slices-and-maps.md            # Backing arrays, append aliasing, map shrinkage
    └── context-patterns.md           # Keys, WithoutCancel, AfterFunc, propagation

Only SKILL.md is loaded on every invocation (~65 lines). Reference files are loaded on-demand based on the task, keeping context usage minimal.

Installation

Cursor — copy into your project or ~/.cursor/skills/ for global use:

cp -r claude/go-guidelines/skills/go-guidelines/ <your-project>/.cursor/skills/go-guidelines/

Claude Code: