golang-grpc

Go gRPC (Production)

Overview

gRPC provides strongly-typed RPC APIs backed by Protocol Buffers, with first-class streaming support and excellent performance for service-to-service communication. This skill focuses on production defaults: versioned protos, deadlines, error codes, interceptors, health checks, TLS, and testability.

Quick Start

1) Define a versioned protobuf API

✅ Correct: versioned package

// proto/users/v1/users.proto
syntax = "proto3";

package users.v1;
option go_package = "example.com/myapp/gen/users/v1;usersv1";

service UsersService {
  rpc GetUser(GetUserRequest) returns (GetUserResponse);
  rpc ListUsers(ListUsersRequest) returns (stream User);
}

message GetUserRequest { string id = 1; }
message GetUserResponse { User user = 1; }
message ListUsersRequest { int32 page_size = 1; string page_token = 2; }

message User {
  string id = 1;
  string email = 2;
  string display_name = 3;
}

❌ Wrong: unversioned package (hard to evolve)

package users;

2) Generate Go code

Install generators:

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

Generate:

protoc -I proto \
  --go_out=./gen --go_opt=paths=source_relative \
  --go-grpc_out=./gen --go-grpc_opt=paths=source_relative \
  proto/users/v1/users.proto

3) Implement server with deadlines and status codes

✅ Correct: validate + map errors to gRPC codes

package usersvc

import (
    "context"

    "google.golang.org/grpc/codes"
    "google.golang.org/grpc/status"

    usersv1 "example.com/myapp/gen/users/v1"
)

type Service struct {
    usersv1.UnimplementedUsersServiceServer
    Repo Repo
}

type Repo interface {
    GetUser(ctx context.Context, id string) (User, error)
}

type User struct {
    ID, Email, DisplayName string
}

func (s *Service) GetUser(ctx context.Context, req *usersv1.GetUserRequest) (*usersv1.GetUserResponse, error) {
    if req.GetId() == "" {
        return nil, status.Error(codes.InvalidArgument, "id is required")
    }

    u, err := s.Repo.GetUser(ctx, req.GetId())
    if err != nil {
        if err == ErrNotFound {
            return nil, status.Error(codes.NotFound, "user not found")
        }
        return nil, status.Error(codes.Internal, "internal error")
    }

    return &usersv1.GetUserResponse{
        User: &usersv1.User{
            Id:          u.ID,
            Email:       u.Email,
            DisplayName: u.DisplayName,
        },
    }, nil
}