Building a Clean & Scalable Golang Architecture: Valuetree Case Study

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Golang has rapidly become one of the most reliable choices for building high-performance backend systems.
In the pursuit of scalability, maintainability, and testability, architecture becomes one of the most important foundations.

The Valuetree project demonstrates a clean and well-structured implementation of Clean Architecture with modular principles, making it an excellent reference for modern Go applications.

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🏗️ Project Structure Overview

Valuetree uses a modular monolith structure:

valuetree/
├── config/
├── internal/
│   ├── domain/
│   ├── handler/
│   ├── model/
│   ├── repository/
│   ├── usecase/
│   ├── pkg/
│   └── user/
├── pkg/
├── go.mod

This ensures clean architectural dependencies:

Handler → Usecase → Repository → Domain/Model

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🧩 Architecture Layers (Clean Architecture)

1. Domain Layer (internal/domain)

The core of the system, containing:

• Entities
• Business rules
• Repository interfaces

It remains fully independent of frameworks or external systems.

type UserRepository interface {
    Create(ctx context.Context, u *User) error
    FindByID(ctx context.Context, id string) (*User, error)
}

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2. Model Layer (internal/model)

Defines:

• DTOs
• Database models
• API request/response schemas

This prevents internal domain structures from leaking to external layers.

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3. Repository Layer (internal/repository)

Responsible for implementing the data access logic.

Because the domain depends only on interfaces, storage engines can be swapped easily (PostgreSQL → MongoDB, etc).

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4. Usecase Layer (internal/usecase)

Contains application-specific business logic, such as:

• User registration flow
• Transaction processing
• Coordination across repositories

This layer is framework-agnostic and highly testable.

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5. Handler Layer (internal/handler)

Responsible for:

• HTTP routing
• Parsing requests
• Calling Usecases
• Returning responses

Handlers stay thin and contain zero business logic.

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👤 Domain Example: internal/user

This domain contains:

• user_handler.go
• user_service.go
• user_repository.go
• user_model.go
• Unit tests

This self-contained structure makes it easy to extend and even migrate to a microservice in the future.

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🛠️ Dependency Injection & Configuration

The config/ directory handles:

• App configuration
• Database initialization
• Wiring of repository → usecase → handler

This ensures consistent environment setup across development, staging, and production.

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🧪 Testing Strategy

Tests included:

handler/user_handler_test.go
user/user_service_test.go

These cover:

• Usecase logic (mocked dependencies)
• Handler behavior (mock usecases)
• Optional repository integration tests

Aligned with Clean Architecture best practices:

Test business rules → test boundaries → test adapters

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🔐 Secure Transaction Flow

Key elements:

• Authentication steps
• Authorization checks
• Input validation
• Logging and auditing
• Layered error handling

This ensures the system stays secure, traceable, and abuse-resistant.

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🚀 Why This Architecture Works

✔ Scalable

Easy to add new domains.

✔ Testable

Usecases are independent and highly testable.

✔ Maintainable

Clear folder boundaries reduce cognitive load.

✔ Flexible

Frameworks, storage, or logging can be replaced with minimal effort.

✔ Future-proof

Designed for modular monolith → microservice migration.