Goa - Design First, Code With Confidence

Goa transforms how you build APIs and microservices in Go with its powerful design-first approach. Instead of writing boilerplate code, you express your API's intent through a clear, expressive DSL. Goa then automatically generates production-ready code, comprehensive documentation, and client libraries—all perfectly aligned with your design.

The result? Dramatically reduced development time, consistent APIs, and the elimination of the documentation-code drift that plagues traditional development.

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Traditional API development suffers from:

• Inconsistency: Manually maintained docs that quickly fall out of sync with code
• Wasted effort: Writing repetitive boilerplate and transport-layer code
• Painful integrations: Client packages that need constant updates
• Design afterthoughts: Documentation added after implementation, missing key details

Goa solves these problems by:

• Generating 30-50% of your codebase directly from your design
• Ensuring perfect alignment between design, code, and documentation
• Supporting multiple transports (HTTP, gRPC, and JSON-RPC) from a single design
• Maintaining a clean separation between business logic and transport details

• Expressive Design Language: Define your API with a clear, type-safe DSL that captures your intent
• Comprehensive Code Generation:
  • Type-safe server interfaces that enforce your design
  • Client packages with full error handling
  • Transport layer adapters (HTTP/gRPC/JSON-RPC) with routing and encoding
  • OpenAPI/Swagger documentation that's always in sync
  • CLI tools for testing your services
• Multi-Protocol Support: Generate HTTP REST, gRPC, and JSON-RPC endpoints from a single design
• Clean Architecture: Business logic remains separate from transport concerns
• Enterprise Ready: Supports authentication, authorization, CORS, logging, and more
• Comprehensive Testing: Includes extensive unit and integration test suites ensuring quality and reliability

┌─────────────┐     ┌──────────────┐     ┌─────────────────────┐
│ Design API  │────>│ Generate Code│────>│ Implement Business  │
│ using DSL   │     │ & Docs       │     │ Logic               │
└─────────────┘     └──────────────┘     └─────────────────────┘

1. Design: Express your API's intent in Goa's DSL
2. Generate: Run goa gen to create server interfaces, client code, and documentation
3. Implement: Focus solely on writing your business logic in the generated interfaces
4. Evolve: Update your design and regenerate code as your API evolves

# Install Goa
go install goa.design/goa/v3/cmd/goa@latest

# Create a new module
mkdir hello && cd hello
go mod init hello

# Define a service in design/design.go
mkdir design
cat > design/design.go << EOF
package design

import . "goa.design/goa/v3/dsl"

var _ = Service("hello", func() {
    Method("say_hello", func() {
        Payload(func() {
            Field(1, "name", String)
            Required("name")
        })
        Result(String)

        HTTP(func() {
            GET("/hello/{name}")
        })
    })
})
EOF

# Generate the code
goa gen hello/design
goa example hello/design

# Build and run
go mod tidy
go run cmd/hello/*.go --http-port 8000

# In another terminal
curl http://localhost:8000/hello/world

The example above:

1. Defines a simple "hello" service with one method
2. Generates server and client code
3. Starts a server that logs requests server-side (without displaying any client output)

For a JSON-RPC service, simply add a JSONRPC expression to the service and method:

var _ = Service("hello" , func() {
    JSONRPC(func() {
        Path("/jsonrpc")
    })
    Method("say_hello", func() {
        Payload(func() {
            Field(1, "name", String)
            Required("name")
        })
        Result(String)

        JSONRPC(func() {})
    })
}

Then test with:

curl -X POST http://localhost:8000/jsonrpc \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"hello.say_hello","params":{"name":"world"},"id":"1"}'

Our documentation site at goa.design provides comprehensive guides and references:

• Introduction: Understand Goa's philosophy and benefits
• Getting Started: Build your first Goa service step-by-step
• Tutorials: Learn to create REST APIs, gRPC services, and more
• Core Concepts: Master the design language and architecture
• Real-World Guide: Follow best practices for production services
• Advanced Topics: Explore advanced features and techniques

The examples repository contains complete, working examples demonstrating:

• Basic: Simple service showcasing core Goa concepts
• Cellar: A more complete REST API example
• Cookies: HTTP cookie management
• Encodings: Working with different content types
• Error: Comprehensive error handling strategies
• Files & Upload/Download: File handling capabilities
• HTTP Status: Custom status code handling
• Interceptors: Request/response processing middleware
• Multipart: Handling multipart form submissions
• Security: Authentication and authorization examples
• Streaming: Implementing streaming endpoints (HTTP, WebSocket, JSON-RPC SSE)
• Tracing: Integrating with observability tools
• TUS: Resumable file uploads implementation

• Join the #goa channel on Gophers Slack
• Ask questions on GitHub Discussions
• Follow us on Bluesky
• Report issues on GitHub
• Find answers with the Goa Guru AI assistant
• Subscribe to our Substack, “Design First”: Design First

MIT License - see LICENSE for details.