seikaikyo/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 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:

// ✅ 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 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
• .gitignore — git ignore patterns. See .gitignore template
• .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.

Tests, Benchmarks, and Examples

Co-locate _test.go files with the code they test. Use testdata/ for fixtures. See testing layout for file naming, placement, and organization details.

Go Workspaces

Use go.work when developing multiple related modules in a monorepo. See workspaces 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. → See samber/cc-skills-golang@golang-refactoring skill for safely moving or splitting existing code into the layout above via type-alias gradual code repair and staged PRs, without a big-bang break.