golang-project-layout
This skill guides Go developers in structuring projects appropriately to their needs, from simple CLI tools to complex services and monorepos. Use it when starting a new Go project, reorganizing existing code, deciding between architectural patterns, setting up workspaces with multiple modules, or choosing directory conventions like cmd/internal/pkg.
git clone --depth 1 https://github.com/samber/cc-skills-golang /tmp/golang-project-layout && cp -r /tmp/golang-project-layout/skills/golang-project-layout ~/.claude/skills/golang-project-layoutSKILL.md
**Persona:** You are a Go project architect. You right-size structure to the problem — a script stays flat, a service gets layers only when justified by actual complexity.
# Go Project Layout
## Architecture Decision: Ask First
When starting a new project, **ask the developer** what software architecture they prefer (clean architecture, hexagonal, DDD, flat structure, etc.). NEVER over-structure small projects — a 100-line CLI tool does not need layers of abstractions or dependency injection.
→ See `samber/cc-skills-golang@golang-design-patterns` skill for detailed architecture guides with file trees and code examples.
## Dependency Injection: Ask Next
After settling on the architecture, **ask the developer** which dependency injection approach they want: manual constructor injection, or a DI library (samber/do, google/wire, uber-go/dig+fx), or none at all. The choice affects how services are wired, how lifecycle (health checks, graceful shutdown) is managed, and how the project is structured. See the `samber/cc-skills-golang@golang-dependency-injection` skill for a full comparison and decision table.
## 12-Factor App
For applications (services, APIs, workers), follow [12-Factor App](https://12factor.net/) conventions: config via environment variables, logs to stdout, stateless processes, graceful shutdown, backing services as attached resources, and admin tasks as one-off commands (e.g., `cmd/migrate/`).
## Quick Start: Choose Your Project Type
| Project Type | Use When | Key Directories |
| --- | --- | --- |
| **CLI Tool** | Building a command-line application | `cmd/{name}/`, `internal/`, optional `pkg/` |
| **Library** | Creating reusable code for others | `pkg/{name}/`, `internal/` for private code |
| **Service** | HTTP API, microservice, or web app | `cmd/{service}/`, `internal/`, `api/`, `web/` |
| **Monorepo** | Multiple related packages/modules | `go.work`, separate modules per package |
| **Workspace** | Developing multiple local modules | `go.work`, replace directives |
## Module Naming Conventions
### Module Name (go.mod)
Your module path in `go.mod` should:
- **MUST match your repository URL**: `github.com/username/project-name`
- **Use lowercase only**: `github.com/you/my-app` (not `MyApp`)
- **Use hyphens for multi-word**: `user-auth` not `user_auth` or `userAuth`
- **Be semantic**: Name should clearly express purpose
**Examples:**
```go
// ✅ Good
module github.com/jdoe/payment-processor
module github.com/company/cli-tool
// ❌ Bad
module myproject
module github.com/jdoe/MyProject
module utils
```
### Package Naming
Packages MUST be lowercase, singular, and match their directory name. → See `samber/cc-skills-golang@golang-naming` skill for complete package naming conventions and examples.
## Directory Layout
All `main` packages must reside in `cmd/` with minimal logic — parse flags, wire dependencies, call `Run()`. Business logic belongs in `internal/` or `pkg/`. Use `internal/` for non-exported packages, `pkg/` only when code is useful to external consumers.
See [directory layout examples](references/directory-layouts.md) for universal, small project, and library layouts, plus common mistakes.
## Essential Configuration Files
Every Go project should include at the root:
- **Makefile** — build automation. See [Makefile template](assets/Makefile)
- **.gitignore** — git ignore patterns. See [.gitignore template](assets/.gitignore)
- **.golangci.yml** — linter config. See the `samber/cc-skills-golang@golang-lint` skill for the recommended configuration
For application configuration with Cobra + Viper, see [config reference](references/config.md).
## Tests, Benchmarks, and Examples
Co-locate `_test.go` files with the code they test. Use `testdata/` for fixtures. See [testing layout](references/testing-layout.md) for file naming, placement, and organization details.
## Go Workspaces
Use `go.work` when developing multiple related modules in a monorepo. See [workspaces](references/workspaces.md) for setup, structure, and commands.
## Initialization Checklist
When starting a new Go project:
- [ ] **Ask the developer** their preferred software architecture (clean, hexagonal, DDD, flat, etc.)
- [ ] **Ask the developer** their preferred DI approach — see `samber/cc-skills-golang@golang-dependency-injection` skill
- [ ] Decide project type (CLI, library, service, monorepo)
- [ ] Right-size the structure to the project scope
- [ ] Choose module name (matches repo URL, lowercase, hyphens)
- [ ] Run `go version` to detect the current go version
- [ ] Run `go mod init github.com/user/project-name`
- [ ] Create `cmd/{name}/main.go` for entry point
- [ ] Create `internal/` for private code
- [ ] Create `pkg/` only if you have public libraries
- [ ] For monorepos: Initialize `go work` and add modules
- [ ] Run `gofmt -s -w .` to ensure formatting
- [ ] Add `.gitignore` with `/vendor/` and binary patterns
## Related Skills
→ See `samber/cc-skills-golang@golang-cli` skill for CLI tool structure and Cobra/Viper patterns. → See `samber/cc-skills-golang@golang-dependency-injection` skill for DI approach comparison and wiring. → See `samber/cc-skills-golang@golang-lint` skill for golangci-lint configuration. → See `samber/cc-skills-golang@golang-continuous-integration` skill for CI/CD pipeline setup. → See `samber/cc-skills-golang@golang-design-patterns` skill for architectural patterns.Golang benchmarking, profiling, and performance measurement. Use when writing, running, or comparing Go benchmarks, profiling hot paths with pprof, interpreting CPU/memory/trace profiles, analyzing results with benchstat, setting up CI benchmark regression detection, or investigating production performance with Prometheus runtime metrics. Also use when the developer needs deep analysis on a specific performance indicator - this skill provides the measurement methodology, while `samber/cc-skills-golang@golang-performance` provides the optimization patterns.
Golang CLI application development. Use when building, modifying, or reviewing a Go CLI tool — especially for command structure, flag handling, configuration layering, version embedding, exit codes, I/O patterns, signal handling, shell completion, argument validation, and CLI unit testing. Also triggers when code uses cobra, viper, or urfave/cli. For cobra-specific APIs → See `samber/cc-skills-golang@golang-spf13-cobra` skill; for viper configuration layering → See `samber/cc-skills-golang@golang-spf13-viper` skill.
Golang code style conventions — line length and breaking, variable declarations, control flow clarity, when comments help vs hurt. Use when writing or reviewing Go code, asking about style or clarity, or establishing project coding standards. Not for naming conventions (→ See `samber/cc-skills-golang@golang-naming` skill), linter configuration (→ See `samber/cc-skills-golang@golang-lint` skill), or doc comments (→ See `samber/cc-skills-golang@golang-documentation` skill).
Golang concurrency patterns. Use when writing or reviewing concurrent Go code involving goroutines, channels, select, locks, sync primitives, errgroup, singleflight, worker pools, or fan-out/fan-in pipelines. Also triggers when you detect goroutine leaks, race conditions, channel ownership issues, or need to choose between channels and mutexes.
Idiomatic context.Context usage in Golang — propagation through API boundaries, cancellation, timeouts and deadlines, request-scoped values, context.WithoutCancel for background work outliving requests. Apply when designing context propagation across layers, debugging leaked or unexpired contexts, choosing between context.Background/TODO/WithoutCancel, or storing values in context. Not for code that merely accepts ctx as first parameter.
CI/CD pipeline configuration using GitHub Actions for Golang projects — testing, linting, SAST, security scanning, code coverage, Dependabot, Renovate, GoReleaser, code review automation, and release pipelines. Use when setting up or improving Go project CI, configuring GitHub Actions workflows, adding linters or security scanners, automating dependency updates, or adding quality gates.
Golang data structures — slices (internals, capacity growth, preallocation, slices package), maps (internals, hash buckets, maps package), arrays, container/list/heap/ring, strings.Builder vs bytes.Buffer, generic collections, pointers (unsafe.Pointer, weak.Pointer), and copy semantics. Use when choosing or optimizing Go data structures, implementing generic containers, using container/ packages, unsafe or weak pointers, or questioning slice/map internals.
Comprehensive guide for Go database access — parameterized queries, struct scanning, NULLable columns, transactions, isolation levels, SELECT FOR UPDATE, connection pool, batch processing, context propagation, and migration tooling. Use when writing, reviewing, or debugging Golang code that interacts with PostgreSQL, MariaDB, MySQL, or SQLite; for database testing; or for questions about database/sql, sqlx, or pgx. Does NOT generate database schemas or migration SQL.