# Golang Grpc

> Ofrece guías de uso de gRPC, organización de protobuf y patrones listos para producción en microservicios Golang: servidores/clientes, proto files, interceptores, códigos de error, TLS/mTLS, bufconn y streaming.

Fuente: https://skillsagentes.com/skills/samber/cc-skills-golang/golang-grpc
Markdown: https://skillsagentes.com/skills/samber/cc-skills-golang/golang-grpc.md

Repositorio: https://github.com/samber/cc-skills-golang
Autor: samber
Licencia: MIT
Actualizado: el mes pasado
Coste de contexto: 85 tok instalada, 2.5k tok al activarse, 8.2k tok con todos los archivos del bundle
Bundle: 4 archivos, 32 KB
Permisos que pide: read edit write glob grep bash(go:*) bash(golangci-lint:*) bash(git:*) agent webfetch mcp__context7__resolve-library-id mcp__context7__query-docs bash(protoc:*) askuserquestion bash(godig:*) bash(gopls:*) lsp mcp__gopls__*

## Instalación

Un skill son archivos markdown: los mismos archivos valen para cualquier agente y lo único que cambia es el directorio de destino, es decir la bandera `--agent`. Añade `-g` para instalarlo en todos los proyectos de la máquina.

```bash
# Claude Code
npx -y skills add samber/cc-skills-golang --skill golang-grpc --agent claude-code
# Cursor
npx -y skills add samber/cc-skills-golang --skill golang-grpc --agent cursor
# Codex
npx -y skills add samber/cc-skills-golang --skill golang-grpc --agent codex
# Gemini CLI
npx -y skills add samber/cc-skills-golang --skill golang-grpc --agent gemini
# Windsurf
npx -y skills add samber/cc-skills-golang --skill golang-grpc --agent windsurf
# Cline
npx -y skills add samber/cc-skills-golang --skill golang-grpc --agent cline
```

## Qué hace

- Aplica patrones de gRPC listos para producción: interceptores, códigos de estado, TLS/mTLS, health checks y graceful shutdown
- Guía la organización de archivos proto por dominio con directorios versionados y mensajes Request/Response
- Corrige errores gRPC comunes: uso de codes.Unknown, falta de deadlines, reflection en producción, etc.
- Recomienda patrones de streaming (server, client, bidireccional) según el caso de uso
- Define cómo testear con bufconn para conexiones en memoria

## Cuándo usarla

- Implementar, revisar o depurar servidores/clientes gRPC
- Escribir archivos proto
- Configurar interceptores, manejo de errores con status codes o TLS/mTLS
- Probar con bufconn o trabajar con RPCs de streaming

## Qué la activa

- "Ayúdame a implementar un servidor gRPC en Go con health checks"
- "Revisa este código gRPC en busca de problemas de seguridad y operabilidad"
- "Cómo estructuro mis archivos proto por dominio"
- "Necesito escribir tests con bufconn para mi servicio gRPC"

## Antes de instalar

- Requiere protoc (brew install protobuf), protoc-gen-go y protoc-gen-go-grpc instalados.

## Archivos

- SKILL.md — 10 KB
- evals/evals.json — 11 KB
- references/protoc-reference.md — 4 KB
- references/testing.md — 7 KB

## SKILL.md

Reproducido tal cual desde samber/cc-skills-golang bajo MIT. Esta sección es el documento original y está en inglés.

**Persona:** You are a Go distributed systems engineer. You design gRPC services for correctness and operability — proper status codes, deadlines, interceptors, and graceful shutdown matter as much as the happy path.

**Modes:**

- **Build mode** — implementing a new gRPC server or client from scratch.
- **Review mode** — auditing existing gRPC code for correctness, security, and operability issues.

**Dependencies:**

- protoc: `brew install protobuf`
- protoc-gen-go: `go install google.golang.org/protobuf/cmd/protoc-gen-go@latest`
- protoc-gen-go-grpc: `go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest`

# Go gRPC Best Practices

Treat gRPC as a pure transport layer — keep it separate from business logic. The official Go implementation is `google.golang.org/grpc`.

This skill is not exhaustive. Please refer to library documentation and code examples for more information. For Go package docs, symbols, versions, importers, and known vulnerabilities, → See `samber/cc-skills-golang@golang-pkg-go-dev` skill (`godig`) — prefer it over Context7 for Go package facts. To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See `samber/cc-skills-golang@golang-gopls` skill (`gopls`). Context7 remains a fallback for docs not indexed on pkg.go.dev.

## Quick Reference

| Concern | Package / Tool |
| --- | --- |
| Service definition | `protoc` or `buf` with `.proto` files |
| Code generation | `protoc-gen-go`, `protoc-gen-go-grpc` |
| Error handling | `google.golang.org/grpc/status` with `codes` |
| Rich error details | `google.golang.org/genproto/googleapis/rpc/errdetails` |
| Interceptors | `grpc.ChainUnaryInterceptor`, `grpc.ChainStreamInterceptor` |
| Middleware ecosystem | `github.com/grpc-ecosystem/go-grpc-middleware` |
| Testing | `google.golang.org/grpc/test/bufconn` |
| TLS / mTLS | `google.golang.org/grpc/credentials` |
| Health checks | `google.golang.org/grpc/health` |

## Proto File Organization

Organize by domain with versioned directories (`proto/user/v1/`). Always use `Request`/`Response` wrapper messages — bare types like `string` cannot have fields added later. Generate with `buf generate` or `protoc`.

[Proto & code generation reference](references/protoc-reference.md)

## Server Implementation

- Implement health check service (`grpc_health_v1`) — Kubernetes probes need it to determine readiness
- Use interceptors for cross-cutting concerns (logging, auth, recovery) — keeps business logic clean
- Use `GracefulStop()` with a timeout fallback to `Stop()` — drains in-flight RPCs while preventing hangs
- Disable reflection in production — it exposes your full API surface

```go
srv := grpc.NewServer(
    grpc.ChainUnaryInterceptor(loggingInterceptor, recoveryInterceptor),
)
pb.RegisterUserServiceServer(srv, svc)
healthpb.RegisterHealthServer(srv, health.NewServer())

go srv.Serve(lis)

// On shutdown signal:
stopped := make(chan struct{})
go func() { srv.GracefulStop(); close(stopped) }()
select {
case <-stopped:
case <-time.After(15 * time.Second):
    srv.Stop()
}
```

### Interceptor Pattern

```go
func loggingInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {
    start := time.Now()
    resp, err := handler(ctx, req)
    log.Printf("method=%s duration=%s code=%s", info.FullMethod, time.Since(start), status.Code(err))
    return resp, err
}
```

## Client Implementation

- Reuse connections — gRPC multiplexes RPCs on a single HTTP/2 connection; one-per-request wastes TCP/TLS handshakes
- Set deadlines on every call (`context.WithTimeout`) — without one, a slow upstream hangs goroutines indefinitely
- Use `round_robin` with headless Kubernetes services via `dns:///` scheme
- Pass metadata (auth tokens, trace IDs) via `metadata.NewOutgoingContext`

```go
conn, err := grpc.NewClient("dns:///user-service:50051",
    grpc.WithTransportCredentials(creds),
    grpc.WithDefaultServiceConfig(`{
        "loadBalancingPolicy": "round_robin",
        "methodConfig": [{
            "name": [{"service": ""}],
            "timeout": "5s",
            "retryPolicy": {
                "maxAttempts": 3,
                "initialBackoff": "0.1s",
                "maxBackoff": "1s",
                "backoffMultiplier": 2,
                "retryableStatusCodes": ["UNAVAILABLE"]
            }
        }]
    }`),
)
client := pb.NewUserServiceClient(conn)
```

## Error Handling

Always return gRPC errors using `status.Error` with a specific code — a raw `error` becomes `codes.Unknown`, telling the client nothing actionable. Clients use codes to decide retry vs fail-fast vs degrade.

| Code                 | When to Use                                 |
| -------------------- | ------------------------------------------- |
| `InvalidArgument`    | Malformed input (missing field, bad format) |
| `NotFound`           | Entity does not exist                       |
| `AlreadyExists`      | Create failed, entity exists                |
| `PermissionDenied`   | Caller lacks permission                     |
| `Unauthenticated`    | Missing or invalid token                    |
| `FailedPrecondition` | System not in required state                |
| `ResourceExhausted`  | Rate limit or quota exceeded                |
| `Unavailable`        | Transient issue, safe to retry              |
| `Internal`           | Unexpected bug                              |
| `DeadlineExceeded`   | Timeout                                     |

```go
// ✗ Bad — caller gets codes.Unknown, can't decide whether to retry
return nil, fmt.Errorf("user not found")

// ✓ Good — specific code lets clients act appropriately
if errors.Is(err, ErrNotFound) {
    return nil, status.Errorf(codes.NotFound, "user %q not found", req.UserId)
}
return nil, status.Errorf(codes.Internal, "lookup failed: %v", err)
```

For field-level validation errors, attach `errdetails.BadRequest` via `status.WithDetails`.

## Streaming

| Pattern | Use Case |
| --- | --- |
| Server streaming | Server sends a sequence (log tailing, result sets) |
| Client streaming | Client sends a sequence, server responds once (file upload, batch) |
| Bidirectional | Both send independently (chat, real-time sync) |

Prefer streaming over large single messages — avoids per-message size limits and lowers memory pressure.

```go
func (s *server) ListUsers(req *pb.ListUsersRequest, stream pb.UserService_ListUsersServer) error {
    for _, u := range users {
        if err := stream.Send(u); err != nil {
            return err
        }
    }
    return nil
}
```

## Testing

Use `bufconn` for in-memory connections that exercise the full gRPC stack (serialization, interceptors, metadata) without network overhead. Always test that error scenarios return the expected gRPC status codes.

[Testing patterns and examples](references/testing.md)

## Security

- TLS MUST be enabled in production — credentials travel in metadata
- For service-to-service auth, use mTLS or delegate to a service mesh (Istio, Linkerd)
- For user auth, implement `credentials.PerRPCCredentials` and validate tokens in an auth interceptor
- Reflection SHOULD be disabled in production to prevent API discovery

## Performance

| Setting | Purpose | Typical Value |
| --- | --- | --- |
| `keepalive.ServerParameters.Time` | Ping interval for idle connections | 30s |
| `keepalive.ServerParameters.Timeout` | Ping ack timeout | 10s |
| `grpc.MaxRecvMsgSize` | Override 4 MB default for large payloads | 16 MB |
| Connection pooling | Multiple conns for high-load streaming | 4 connections |

Most services do not need connection pooling — profile before adding complexity.

## Common Mistakes

| Mistake | Fix |
| --- | --- |
| Returning raw `error` | Becomes `codes.Unknown` — client can't decide whether to retry. Use `status.Errorf` with a specific code |
| No deadline on client calls | Slow upstream hangs indefinitely. Always `context.WithTimeout` |
| New connection per request | Wastes TCP/TLS handshakes. Create once, reuse — HTTP/2 multiplexes RPCs |
| Reflection enabled in production | Lets attackers enumerate every method. Enable only in dev/staging |
| `codes.Internal` for all errors | Wrong codes break client retry logic. `Unavailable` triggers retry; `InvalidArgument` does not |
| Bare types as RPC arguments | Can't add fields to `string`. Wrapper messages allow backwards-compatible evolution |
| Missing health check service | Kubernetes can't determine readiness, kills pods during deployments |
| Ignoring context cancellation | Long operations continue after caller gave up. Check `ctx.Err()` |

## Cross-References

- → See `samber/cc-skills-golang@golang-context` skill for deadline and cancellation patterns
- → See `samber/cc-skills-golang@golang-error-handling` skill for gRPC error to Go error mapping
- → See `samber/cc-skills-golang@golang-observability` skill for gRPC interceptors (logging, tracing, metrics)
- → See `samber/cc-skills-golang@golang-testing` skill for gRPC testing with bufconn

## Dónde encaja

- Categoría: [Desarrollo de APIs](https://skillsagentes.com/categorias/desarrollo-apis.md) — Diseña, prueba y documenta APIs HTTP y GraphQL.
- Creador: [samber](https://skillsagentes.com/creators/samber.md) — 0 skills en el directorio
- [Todas las skills](https://skillsagentes.com/skills.md)
- [Ranking de instalaciones](https://skillsagentes.com/ranking.md)

## Otras skills del mismo repositorio

- [Golang Lint](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-lint.md): Buenas prácticas de linting y configuración de golangci-lint para proyectos Golang: ejecutar linters, configurar .golangci.yml, suprimir avisos con nolint, interpretar salidas y elegir linters.
- [Golang How To](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-how-to.md): Orquestador de skills de Golang, siempre activo en cualquier tarea de código, revisión, debug o setup: carga las skills más relevantes de samber/cc-skills-golang, a menudo varias a la vez.
- [Golang Benchmark](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-benchmark.md): Benchmarking, profiling y medición de rendimiento en Golang: escribir y comparar benchmarks, perfilar con pprof, analizar con benchstat y detectar regresiones en CI.
- [Golang Testing](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-testing.md): Tests de Golang listos para producción: table-driven, suites y mocks con testify, tests paralelos, fuzzing, fixtures, detección de fugas de goroutines con goleak, snapshot testing, cobertura, tests de integración.
- [Golang Performance](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-performance.md): Patrones y metodología de optimización de rendimiento en Golang: si hay cuello de botella X, aplica el patrón Y, una vez que profiling o benchmarks ya lo identificaron.

## Skills relacionadas

- [Golang Graphql](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-graphql.md): Implementa APIs GraphQL en Golang con gqlgen o graphql-go: diseño de schemas, resolvers, suscripciones e integración con servicios HTTP en Go.
- [Golang Swagger](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-swagger.md): Documentación OpenAPI/Swagger en Go con swaggo/swag: anotaciones, `swag init`, integraciones con gin/echo/fiber/chi/net/http, seguridad y etiquetas de struct.
- [Golang Uber Dig](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-uber-dig.md): Implementa inyección de dependencias en Golang con uber-go/dig: contenedor basado en reflexión, Provide/Invoke, dig.In/dig.Out, valores nombrados, value groups, dependencias opcionales, scopes y Decorate.
- [Golang Safety](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-safety.md): Codificación defensiva en Golang para evitar panics, corrupción silenciosa de datos y bugs sutiles en tiempo de ejecución.
- [Golang Samber Hot](https://skillsagentes.com/skills/samber/cc-skills-golang/golang-samber-hot.md): Caché en memoria en Golang con samber/hot: algoritmos de expulsión (LRU, LFU, TinyLFU, S3FIFO, ARC, TwoQueue, SIEVE, FIFO), TTL, loaders, sharding y métricas Prometheus.

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