Connect RPC API Boilerplate

This is a boilerplate repository for building Go APIs using Connect RPC and Buf. It demonstrates a protocol-first development approach where all interactions with the system are driven through protobuf service definitions.

My recommendation is to develop as though any service could be deployed separately from other services, even if the whole project is deployed as a monolith. This will make breaking individual services into its own deployment simpler, if the need arises. If you only call across service boundaries using the interfaces defined in proto/, then the contract doesn't change when you break out a service.

A basic example service user is defined with two stores - sqlite and dynamodb.

• The public interface is defined in proto/user/v1/.
• The handlers are defined in internal/services/user/
• The stores are defined in internal/services/user/store
• The server registers the handlers in internal/server/user_connect_handler.go

Architecture Philosophy

Schema-First Development: This boilerplate enforces that all access to business logic and data must flow through the protobuf-defined service interface. There are no direct paths to business logic or database operations outside of what's explicitly defined in the .proto files.

This approach ensures:

• API Contract Clarity: The protobuf definitions serve as the single source of truth for what the API can do
• Type Safety: All data structures and service methods are strongly typed
• Multi-Language Support: Connect RPC works with any language that supports protobuf
• Backwards Compatibility: Changes to the API can be validated for breaking changes using buf

Getting Started

First-Time Setup (Required)

IMPORTANT: If you've copied or forked this repository, run the setup script once to rename the project:

./setup.sh your.domain.com/username/project-name

For example:

./setup.sh github.com/myuser/my-api
./setup.sh git.company.com/team/project-api

This script will:

• Update all Go imports from github.com/andrew-womeldorf/connect-boilerplate to your module name
• Update all configuration files (go.mod, buf.gen.yaml, etc.)

After running setup:

1. Generate protobuf code: mise run proto:generate
2. Run quality checks: mise run check
3. Commit your changes: git add . && git commit -m "Rename project to your-module-name"
4. Remove setup script: rm setup.sh

Development Workflow

1. Trust mise configuration: mise trust
2. Generate protobuf code: mise run proto:generate
3. Start the server: mise run serve
4. Test with RPC commands: ./build/api user list-users (after building)

Directory Structure

proto/

The Source of Truth - Contains all protobuf definitions using the 1-1-1 pattern:

• proto/user/v1/user_service.proto - Service definition (imports all message types)
• proto/user/v1/user.proto - Core entity definitions
• proto/user/v1/{operation}.proto - Individual request/response message pairs

Key Principle: All functionality must be defined here first. No business logic should exist without a corresponding protobuf definition.

gen/

Generated Code - Auto-generated Go code from protobuf definitions. Never edit manually.

• gen/user/v1/*.pb.go - Protobuf message types
• gen/user/v1/userv1connect/*.connect.go - Connect RPC service interfaces

internal/services/user/

Business Logic Layer - Implements the actual service logic defined in protobuf.

• service.go - Core business logic that implements the protobuf-generated interfaces
• Methods must match exactly what's defined in the .proto service definitions

internal/server/

HTTP Server Layer - Bridges the business logic to HTTP transport and handles data access.

• server.go - HTTP server setup with Connect RPC handlers, gRPC reflection, and h2c support
• user_connect_handler.go - Thin adapter that connects internal/services/user service to Connect RPC interface
• Provides both standalone server (Run()) and handler creation (CreateHandler()) for Lambda
• Database Access: All data persistence should be handled at this layer

cmd/

Entry Points - Two distinct deployment targets:

cmd/cli/

CLI Interface - Cobra-based command-line tool with dual-mode operation:

• serve.go - Starts the HTTP server
• user.go - User RPC client setup with endpoint configuration
• user_*.go - Individual User RPC command implementations (one file per RPC method)

Dual Mode Support:

• In-memory mode (default): Directly calls service methods for testing/development
• Remote mode (--endpoint flag): Makes HTTP Connect RPC calls to running server

cmd/lambda/

AWS Lambda Entry Point - Uses the same server handler for serverless deployment.

Configuration Files

• buf.yaml & buf.gen.yaml - Buf configuration for protobuf linting and code generation
• mise.toml - Task runner configuration for development workflows
• go.mod - Go module with Connect RPC and related dependencies

Development Workflow

1. Define the API: Start by defining or modifying .proto files in proto/
2. Generate Code: Run mise run proto:generate to update generated code
3. Implement Business Logic: Add implementation in internal/services/<svc>/service.go
4. Update Adapter: Ensure internal/server/<svc>_connect_handler.go routes to your service methods
5. Test: Use CLI commands or start server to test functionality

Key Commands

• mise run proto:generate - Regenerate code from protobuf definitions
• mise run serve - Start development server on port 8088
• mise run check - Run all linters, formatters, and tests
• mise run build - Build CLI binary to build/api

Protocol-First Enforcement

This boilerplate is designed to prevent common anti-patterns:

• ❌ Don't: Create RPC methods that bypass the protobuf service definitions

• ❌ Don't: Add database access outside of the pkg/api layer

• ❌ Don't: Create business logic that isn't exposed through a protobuf RPC method

• ✅ Do: Define all functionality in .proto files first

• ✅ Do: Implement business logic in pkg/api/service.go methods

• ✅ Do: Use the CLI RPC commands for testing and client interaction

This ensures your API remains consistent, type-safe, and evolvable while supporting multiple deployment targets (HTTP server, Lambda, CLI).