Go API Starter 🚀

Production-ready Go REST & gRPC API starter template with JWT authentication, Kubernetes deployment, Clean Architecture, and a Rust CLI client.

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✨ Key Features

Category	Features
Authentication	JWT with refresh tokens, bcrypt password hashing, RBAC (Admin/User/Viewer)
Architecture	Clean Architecture (Handler → Service → Repository), Dependency Injection
API	REST (Echo v4) + gRPC with streaming, OpenAPI 3.1 specification
Resilience	Circuit breaker, retry with exponential backoff, rate limiting, graceful shutdown
Observability	OpenTelemetry tracing (Jaeger), Prometheus metrics, structured logging (slog), audit logs
Infrastructure	Docker, Kubernetes manifests with Kustomize (dev/prod), GitHub Actions CI/CD
Developer Tools	Rust CLI client, Dev Container, Taskfile, pre-commit hooks, sqlc
Go Patterns	Generics (Result/Option types), Worker Pool, Context utilities, Type-safe errors

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🏗️ Architecture

┌─────────────────────────────────────────────────────────────────────────────┐
│                           Transport Layer                                    │
│  ┌───────────────────────────────┐  ┌───────────────────────────────┐       │
│  │         REST (Echo)           │  │       gRPC (grpc-go)          │       │
│  │  Port 8080                    │  │  Port 9090                    │       │
│  │  /api/v1/todos, /health       │  │  TodoService (streaming)      │       │
│  └───────────────────────────────┘  └───────────────────────────────┘       │
└─────────────────────────────────────────────────────────────────────────────┘
                                    ↓
┌─────────────────────────────────────────────────────────────────────────────┐
│                            Middleware Chain                                  │
│  RequestID → Logger → Recovery → RateLimiter → Auth → RBAC                  │
└─────────────────────────────────────────────────────────────────────────────┘
                                    ↓
┌─────────────────────────────────────────────────────────────────────────────┐
│                            Handler Layer                                     │
│  Request validation, response formatting, error mapping to HTTP/gRPC codes  │
└─────────────────────────────────────────────────────────────────────────────┘
                                    ↓
┌─────────────────────────────────────────────────────────────────────────────┐
│                            Service Layer                                     │
│  Business logic, JWT generation, password hashing, authorization checks      │
└─────────────────────────────────────────────────────────────────────────────┘
                                    ↓
┌─────────────────────────────────────────────────────────────────────────────┐
│                           Repository Layer                                   │
│  Data access interfaces, PostgreSQL implementation (sqlc generated)         │
└─────────────────────────────────────────────────────────────────────────────┘
                                    ↓
┌─────────────────────────────────────────────────────────────────────────────┐
│                             PostgreSQL                                       │
│  users (id, email, password_hash, role) ←──→ todos (id, user_id, title...)  │
└─────────────────────────────────────────────────────────────────────────────┘

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📁 Project Structure

go-api-starter/
├── cmd/server/              # Application entry point with graceful shutdown
├── internal/
│   ├── config/              # Configuration management (env, validation)
│   ├── handler/             # HTTP handlers (REST controllers)
│   ├── grpc/                # gRPC server and service implementations
│   ├── middleware/          # Custom middleware (auth, logging, rate limit)
│   ├── model/               # Domain models
│   ├── repository/          # Data access layer (interfaces + implementations)
│   └── service/             # Business logic layer
├── pkg/                     # Reusable packages (see below)
│   ├── apperrors/           # Custom error types with Is/As support
│   ├── cache/               # Generic in-memory cache with TTL/LRU
│   ├── circuitbreaker/      # Circuit breaker pattern
│   ├── generic/             # Result/Option types, functional helpers
│   ├── healthcheck/         # K8s-ready health check system
│   ├── metrics/             # Prometheus metrics
│   ├── rbac/                # Role-based access control
│   ├── resilience/          # Retry, timeout, fallback patterns
│   ├── retry/               # Exponential backoff with jitter
│   ├── token/               # JWT token generation/validation
│   ├── tracing/             # OpenTelemetry integration
│   └── workerpool/          # Concurrent task processing
├── api/grpc/                # Protocol Buffers definitions
├── gen/go/                  # Generated gRPC code (buf)
├── deploy/
│   └── k8s/                 # Kubernetes manifests
│       ├── base/            # Base manifests (Deployment, Service, HPA, etc.)
│       └── overlays/        # Environment-specific (development, production)
├── tools/
│   └── todo-cli/            # Rust CLI client for the API
├── db/
│   ├── migrations/          # SQL migrations
│   └── queries/             # sqlc query definitions
├── docs/
│   ├── adr/                 # Architecture Decision Records
│   └── openapi.yaml         # OpenAPI 3.1 specification
└── .github/workflows/       # CI/CD pipelines

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🚀 Quick Start

Prerequisites

• Go 1.22+
• Docker & Docker Compose
• (Optional) Task for development commands

Option 1: Docker Compose (Recommended)

# Clone and start all services
git clone https://github.com/hassan123789/go-api-starter.git
cd go-api-starter
docker-compose up -d

# API available at http://localhost:8080
# gRPC available at localhost:9090

Option 2: Local Development

# Clone repository
git clone https://github.com/hassan123789/go-api-starter.git
cd go-api-starter

# Setup environment
cp .env.example .env

# Start PostgreSQL
docker-compose up -d postgres

# Run migrations
export DATABASE_URL="postgres://postgres:postgres@localhost:5432/go_api_starter?sslmode=disable"
task migrate  # or: make migrate

# Start server (with hot reload)
task run      # or: make run

Option 3: Dev Container (VS Code)

1. Open the project in VS Code
2. Click "Reopen in Container" when prompted
3. All tools and dependencies are pre-configured

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🔌 API Reference

REST Endpoints

Method	Endpoint	Description	Auth
GET	/health	Full health check with dependencies	❌
GET	/livez	Kubernetes liveness probe	❌
GET	/readyz	Kubernetes readiness probe	❌
GET	/metrics	Prometheus metrics	❌
POST	/api/v1/users	Register new user	❌
POST	/api/v1/auth/login	Login, returns JWT	❌
POST	/api/v1/auth/refresh	Refresh access token	✅
GET	/api/v1/todos	List todos (paginated)	✅
POST	/api/v1/todos	Create todo	✅
GET	/api/v1/todos/:id	Get todo by ID	✅
PUT	/api/v1/todos/:id	Update todo	✅
DELETE	/api/v1/todos/:id	Delete todo	✅

gRPC Service

service TodoService {
  rpc CreateTodo(CreateTodoRequest) returns (Todo);
  rpc GetTodo(GetTodoRequest) returns (Todo);
  rpc ListTodos(ListTodosRequest) returns (ListTodosResponse);
  rpc UpdateTodo(UpdateTodoRequest) returns (Todo);
  rpc DeleteTodo(DeleteTodoRequest) returns (google.protobuf.Empty);
  rpc StreamTodos(StreamTodosRequest) returns (stream TodoEvent);  // Real-time updates
}

Example Usage

# Register a user
curl -X POST http://localhost:8080/api/v1/users \
  -H "Content-Type: application/json" \
  -d '{"email": "[email protected]", "password": "securepass123"}'

# Login
TOKEN=$(curl -s -X POST http://localhost:8080/api/v1/auth/login \
  -H "Content-Type: application/json" \
  -d '{"email": "[email protected]", "password": "securepass123"}' | jq -r '.token')

# Create a todo
curl -X POST http://localhost:8080/api/v1/todos \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $TOKEN" \
  -d '{"title": "Learn Go patterns", "description": "Study clean architecture"}'

# List todos
curl http://localhost:8080/api/v1/todos \
  -H "Authorization: Bearer $TOKEN"

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🦀 Rust CLI Client

A native CLI tool for interacting with the API:

# Build the CLI
cd tools/todo-cli
cargo build --release

# Configure API endpoint
./target/release/todo-cli config set-url http://localhost:8080

# Authenticate
./target/release/todo-cli auth login

# Manage todos
./target/release/todo-cli list
./target/release/todo-cli create --title "New task" --description "Details"
./target/release/todo-cli done 1
./target/release/todo-cli delete 1

# JSON output for scripting
./target/release/todo-cli list --format json

---

☸️ Kubernetes Deployment

Production-ready Kubernetes manifests with Kustomize:

# Preview development deployment
kubectl kustomize deploy/k8s/overlays/development

# Preview production deployment
kubectl kustomize deploy/k8s/overlays/production

# Apply to cluster
kubectl apply -k deploy/k8s/overlays/production

Included Resources

Resource	Description
Deployment	Rolling updates, resource limits, security context (non-root)
Service	ClusterIP for internal communication
HPA	Auto-scaling (3-20 replicas based on CPU/memory)
PDB	Pod disruption budget (minAvailable: 2)
Ingress	With cert-manager TLS annotations
NetworkPolicy	Restrict traffic to namespace
ConfigMap	Environment configuration
Secret	Sensitive data (JWT secret, DB credentials)

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📦 Reusable Packages (pkg/)

Error Handling (pkg/apperrors)

import "github.com/hassan123789/go-api-starter/pkg/apperrors"

// Create typed errors
err := apperrors.NewNotFound("todo", todoID)
err := apperrors.NewValidation("email", "invalid format")
err := apperrors.NewUnauthorized("invalid credentials")

// Check error types (works with errors.Is)
if errors.Is(err, apperrors.ErrNotFound) {
    // Handle not found
}

// Automatic HTTP status mapping
status := apperrors.GetHTTPStatus(err) // 404, 400, 401, etc.

Generic Utilities (pkg/generic)

import "github.com/hassan123789/go-api-starter/pkg/generic"

// Result type (Rust-like error handling)
result := generic.Ok(fetchData())
if result.IsOk() {
    data := result.Unwrap()
}
errorResult := generic.Err[int](errors.New("failed"))

// Option type
opt := generic.Some("value")
value := opt.UnwrapOr("default")

// Functional helpers
numbers := []int{1, 2, 3, 4, 5}
evens := generic.Filter(numbers, func(n int) bool { return n%2 == 0 })
doubled := generic.MapSlice(numbers, func(n int) int { return n * 2 })
sum := generic.Reduce(numbers, 0, func(acc, n int) int { return acc + n })

Circuit Breaker (pkg/circuitbreaker)

import "github.com/hassan123789/go-api-starter/pkg/circuitbreaker"

cb := circuitbreaker.New(circuitbreaker.Options{
    MaxFailures:   5,
    Timeout:       30 * time.Second,
    HalfOpenLimit: 3,
})

err := cb.Execute(ctx, func(ctx context.Context) error {
    return callExternalService(ctx)
})

// With fallback
result, err := cb.ExecuteWithFallback(ctx, primaryFn, fallbackFn)

Worker Pool (pkg/workerpool)

import "github.com/hassan123789/go-api-starter/pkg/workerpool"

// Process items concurrently
results, errors := workerpool.Process(ctx, 10, items, func(ctx context.Context, item Item) (Result, error) {
    return processItem(ctx, item)
})

// Pipeline processing
pipeline := workerpool.NewPipeline[Data]().
    AddStage(validate).
    AddStage(transform).
    AddStage(enrich)

result, err := pipeline.Execute(ctx, input)

---

🛠️ Development

Available Commands

# Using Taskfile (recommended)
task            # Show all available tasks
task build      # Build binary
task test       # Run tests
task lint       # Run golangci-lint (50+ linters)
task check      # Run all checks (lint, test, vet)
task docker:up  # Start Docker services
task proto      # Regenerate gRPC code

# Using Makefile (alternative)
make help       # Show all commands
make build      # Build binary
make test       # Run tests with coverage
make lint       # Run linter

Testing

# Run all tests
task test

# Run with coverage report
task test:coverage

# Run specific package tests
go test -v ./pkg/circuitbreaker/...

# Run benchmarks
task bench

Code Quality

# Lint with 50+ rules
task lint

# Format code
task fmt

# Security scan
task sec

# Pre-commit hooks (auto-run on commit)
pre-commit install
pre-commit run --all-files

---

🔧 Configuration

Variable	Description	Default
PORT	HTTP server port	8080
GRPC_PORT	gRPC server port	9090
GRPC_ENABLED	Enable gRPC server	true
DATABASE_URL	PostgreSQL connection string	-
JWT_SECRET	JWT signing key	-
JWT_EXPIRY	Access token expiry	24h
JWT_REFRESH_EXPIRY	Refresh token expiry	168h
LOG_LEVEL	Log level (debug/info/warn/error)	info
OTEL_EXPORTER_JAEGER_ENDPOINT	Jaeger collector URL	-

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📚 Documentation

Document	Description
API Specification	OpenAPI 3.1 specification
Architecture Decisions	ADRs explaining design choices
Architecture Guide	Deep dive into design decisions
Contributing Guide	How to contribute
Security Policy	Reporting vulnerabilities
Kubernetes Guide	Deployment instructions

Architecture Decision Records (ADR)

ADR	Title
001	Adopting Clean Architecture
002	Choosing Echo Framework
003	JWT Authentication Strategy
004	Error Handling Design
005	OpenTelemetry Tracing
006	RBAC Strategy
007	Resilience Patterns
008	Audit Logging

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🤝 Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/amazing-feature)
3. Write tests for your changes
4. Ensure all checks pass (task check)
5. Commit with conventional commits (git commit -m 'feat: add amazing feature')
6. Push to your branch (git push origin feature/amazing-feature)
7. Open a Pull Request

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📄 License

MIT License - see LICENSE for details.

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