Go Backend Best Practices

Purpose

Apply Go backend patterns for building production-ready services.

Rules

1. Project Structure (Standard Layout)

layout: "cmd/{server/main.go} + internal/{handler/,service/,repository/,model/} + pkg/{shared/} + api/{openapi.yaml} + configs/ + scripts/"

directories:
  cmd: Main applications (one per binary)
  internal: Private application code
  pkg: Library code safe for external use
  api: API definitions (OpenAPI, protobuf)
  configs: Configuration files
  scripts: Build and CI scripts

Reference: guides/go-backend/project-layout.md

2. Error Handling (Uber Style)

principles:
  - Wrap errors with context using %w
  - Handle errors once (don't log AND return)
  - Use sentinel errors for specific conditions
  - Name error variables with Err prefix

patterns:
  sentinel: "var ErrNotFound = errors.New(\"not found\")"
  wrapping: "fmt.Errorf(\"getUser %s: %w\", id, err)"
  checking: "errors.Is(err, ErrNotFound)"

Reference: guides/go-backend/uber-style.md

3. Concurrency (Uber Style)

channels:
  size: "Use 0 (unbuffered) or 1 only"
  larger: "Requires careful review"

goroutines:
  never: fire-and-forget
  always: wait for completion or manage lifecycle
  patterns: "sync.WaitGroup + error channel for parallel work; context.Context for cancellation"

Reference: guides/go-backend/uber-style.md

4. HTTP Server

structure:
  handler: HTTP layer (request/response)
  service: Business logic
  repository: Data access

patterns:
  dependency_injection: "Handler struct with service field, constructor NewXxxHandler()"
  router: "chi.NewRouter() with middleware (Logger, Recoverer) and versioned routes"
  error_mapping: "errors.Is() to map domain errors to HTTP status codes"

Reference: guides/go-backend/uber-style.md

5. Dependency Injection

approach: constructor injection
avoid: global variables
pattern: "Struct with dependencies as fields, New* constructor functions, wire up in main()"

Reference: guides/go-backend/uber-style.md

6. Configuration

approach:
  - Use environment variables
  - Validate at startup
  - Group related settings
pattern: "Config struct with nested typed configs, env struct tags, Parse at startup"

Reference: guides/go-backend/uber-style.md

7. Testing

patterns:
  table_driven: for comprehensive coverage
  interfaces: for mocking
  parallel: for speed
  tools: "gomock for mocks, cmp.Diff for assertions"

Reference: guides/go-backend/uber-style.md

8. Performance (Uber Style)

guidelines:
  - Use strconv over fmt for conversions
  - Pre-allocate slices with known capacity
  - Avoid repeated string-to-byte conversions
  - Copy slices/maps at boundaries

Reference: guides/go-backend/uber-style.md

Application

When writing Go backend code:

1. Always use standard project layout
2. Always wrap errors with context
3. Never fire-and-forget goroutines
4. Use constructor injection
5. Use table-driven tests
6. Handle errors once
7. Copy data at boundaries
8. Validate config at startup

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