Golang Patterns

Golang Patterns

Idiomatic Go reference pack — concurrency, interfaces, generics, testing, project structure, plus the anti-patterns agents most commonly get wrong. Two-thesis stack:

• Clear is better than clever. Boring, explicit, maintainable Go (Jon Bodner, Learning Go, 2nd ed.).
• Production-grade by default. Bounded goroutine lifetimes, context threading, race-detector-clean tests, gofmt + golangci-lint on every change.

Reference Guide

Load detailed guidance based on context:

Core Workflow

1. Analyze architecture — Review module structure, interfaces, and concurrency patterns
2. Design interfaces — Small, focused, defined at the consumer; composition over inheritance
3. Implement — Idiomatic Go with proper error handling and context propagation; run go vet ./... before proceeding
4. Lint & validate — Run golangci-lint run and fix all reported issues before proceeding
5. Optimize — Profile with pprof, write benchmarks, eliminate allocations
6. Test — Table-driven tests with -race, fuzzing, 80%+ coverage; race detector must pass before committing

Core Pattern Example

Goroutine with context cancellation and error propagation:

// worker runs until ctx is cancelled or an error occurs.
// Errors are returned via errCh; the caller must drain it.
func worker(ctx context.Context, jobs <-chan Job, errCh chan<- error) {
    for {
        select {
        case <-ctx.Done():
            errCh <- fmt.Errorf("worker cancelled: %w", ctx.Err())
            return
        case job, ok := <-jobs:
            if !ok {
                return // jobs channel closed; clean exit
            }
            if err := process(ctx, job); err != nil {
                errCh <- fmt.Errorf("process job %v: %w", job.ID, err)
                return
            }
        }
    }
}

func runPipeline(ctx context.Context, jobs []Job) error {
    ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
    defer cancel()

    jobCh := make(chan Job, len(jobs))
    errCh := make(chan error, 1)

    go worker(ctx, jobCh, errCh)

    for _, j := range jobs {
        jobCh <- j
    }
    close(jobCh)

    select {
    case err := <-errCh:
        return err
    case <-ctx.Done():
        return fmt.Errorf("pipeline timed out: %w", ctx.Err())
    }
}

Key properties: bounded goroutine lifetime via ctx, error propagation with %w, no goroutine leak on cancellation.

Constraints

MUST DO

• Run gofmt and golangci-lint on all code
• Add context.Context as first param on all blocking operations
• Handle every error explicitly (no naked _ discards without justification)
• Write table-driven tests with subtests
• Document all exported functions, types, and packages
• Use X | Y union constraints for generics (Go 1.18+)
• Propagate errors with fmt.Errorf("...: %w", err)
• Run race detector on tests (-race flag)

MUST NOT DO

• Ignore errors (no _ = thatMightFail() without a comment)
• Use panic for normal error handling
• Spawn goroutines without a clear lifecycle
• Skip context cancellation handling
• Reach for reflection without a measured performance reason
• Mix sync and async patterns carelessly
• Hardcode configuration (functional options or env vars)

Output Templates

When implementing Go features, provide:

1. Interface definitions (contracts first)
2. Implementation files with proper package structure
3. Test file with table-driven tests
4. Brief explanation of any concurrency patterns used

Pairing

• golang-pro agent — broader architectural / DevOps coverage; delegates pattern detail here. Load both when active Go development is in scope.

Provenance

Initial content adapted from jeffallan/claude-skills (MIT, skills/golang-pro) and the prior wardrobe idiomatic-go skill (Bodner-derived anti-pattern tables, now at references/idiomatic-go.md). See LICENSES.md.