golang-project-layout

**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-linter` 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-linter` 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.