Moai Lang Go

Go Systems Development — Enterprise v4.0

Technology Stack (November 2025 Stable)

Language & Runtime

• Go 1.25.4 (November 2025, compiler & runtime improvements)
• Unix/Linux first with Windows/macOS support
• Garbage collection with concurrent sweeper

Web Frameworks

• Fiber v3.x (Express.js-inspired, high performance)
• Echo 4.13.x (Scalable, middleware-rich)
• Chi 5.x (Lightweight, composable)

Concurrency & RPC

• goroutines (lightweight threads, stdlib)
• channels (typed message passing)
• gRPC 1.67 (Protocol buffers, streaming)
• Protobuf 3.21 (Message serialization)

Data Access

• sqlc 1.26 (Type-safe SQL code generation)
• pgx 5.7 (PostgreSQL driver with pooling)
• context (Request-scoped data, timeouts)

Testing & Quality

• testing (stdlib testing package)
• testify 1.9 (Assertions, mocking, suites)
• benchmarking (Built-in performance testing)

Level 1: Quick Reference

Go Fundamentals

Variables & Types:

// Type declarations
var name string = "John"
var age int = 30
price := 19.99  // Type inference

// Structs
type User struct {
    ID    int
    Name  string
    Email string
}

// Interfaces
type Reader interface {
    Read(p []byte) (n int, err error)
}

Functions & Error Handling:

// Basic function
func Greet(name string) string {
    return "Hello, " + name
}

// Multiple return values
func Divide(a, b float64) (float64, error) {
    if b == 0 {
        return 0, errors.New("division by zero")
    }
    return a / b, nil
}

// Error handling
result, err := Divide(10, 0)
if err != nil {
    log.Fatal(err)
}

HTTP Server with Fiber

Quick REST API:

package main

import "github.com/gofiber/fiber/v3"

func main() {
    app := fiber.New()

    // GET handler
    app.Get("/users", func(c fiber.Ctx) error {
        return c.JSON(fiber.Map{"users": []string{"John", "Jane"}})
    })

    // POST handler
    app.Post("/users", func(c fiber.Ctx) error {
        type User struct {
            Name  string `json:"name"`
            Email string `json:"email"`
        }

        var user User
        if err := c.BodyParser(&user); err != nil {
            return c.Status(fiber.StatusBadRequest).SendString(err.Error())
        }

        return c.Status(fiber.StatusCreated).JSON(user)
    })

    // Route parameters
    app.Get("/users/:id", func(c fiber.Ctx) error {
        id := c.Params("id")
        return c.SendString("User: " + id)
    })

    app.Listen(":3000")
}

Context & Cancellation

Timeout Context:

package main

import "context"

ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()

// Use context for operations
select {
case <-ctx.Done():
    fmt.Println("Operation cancelled:", ctx.Err())
case <-time.After(5 * time.Second):
    fmt.Println("Operation completed")
}

Context with Values:

ctx := context.WithValue(context.Background(), "user_id", "123")

// Retrieve value
userID, ok := ctx.Value("user_id").(string)
if ok {
    fmt.Println("User:", userID)
}

Goroutines & Channels

Basic Concurrency:

// Start goroutine
go func() {
    fmt.Println("Running concurrently")
}()

// Channels
ch := make(chan int)
go func() {
    ch <- 42
}()
value := <-ch

// Close channel
close(ch)

Worker Pool Pattern:

func worker(id int, jobs <-chan int, results chan<- int) {
    for job := range jobs {
        results <- job * 2
    }
}

func main() {
    jobs := make(chan int, 100)
    results := make(chan int, 100)

    // Start 3 workers
    for w := 1; w <= 3; w++ {
        go worker(w, jobs, results)
    }

    // Send jobs and collect results
    for j := 1; j <= 9; j++ {
        jobs <- j
    }
    close(jobs)
}

Level 2: Core Implementation

Type-Safe SQL with sqlc

Queries:

-- queries.sql
-- name: GetUser :one
SELECT id, name, email FROM users WHERE id = $1;

-- name: CreateUser :one
INSERT INTO users (name, email) VALUES ($1, $2)
RETURNING id, name, email;

-- name: ListUsers :many
SELECT id, name, email FROM users ORDER BY id;

Usage:

db := New(pool)
ctx := context.Background()

// Create user
user, _ := db.CreateUser(ctx, CreateUserParams{
    Name:  "John",
    Email: "john@example.com",
})

// Get user
user, _ := db.GetUser(ctx, 1)

// List users
users, _ := db.ListUsers(ctx)

Middleware with Fiber

app.Use(func(c fiber.Ctx) error {
    fmt.Println("Before handler")
    err := c.Next()
    fmt.Println("After handler")
    return err
})

app.Get("/protected", AuthMiddleware, func(c fiber.Ctx) error {
    return c.SendString("Protected route")
})

Advanced Error Handling

type AppError struct {
    Code    int
    Message string
    Details string
}

func (e *AppError) Error() string {
    return fmt.Sprintf("Error %d: %s - %s", e.Code, e.Message, e.Details)
}

func NewAppError(code int, message, details string) *AppError {
    return &AppError{
        Code:    code,
        Message: message,
        Details: details,
    }
}

// Usage in handler
app.Get("/error", func(c fiber.Ctx) error {
    err := NewAppError(500, "Internal Error", "Database connection failed")
    return c.Status(err.Code).JSON(err)
})

Level 3: Advanced Features

gRPC Services

Protocol Buffer Definition:

// user.proto
syntax = "proto3";

package user;

option go_package = "./pb";

service UserService {
  rpc GetUser(GetUserRequest) returns (GetUserResponse);
  rpc ListUsers(ListUsersRequest) returns (ListUsersResponse);
}

message GetUserRequest {
  int32 id = 1;
}

message GetUserResponse {
  int32 id = 1;
  string name = 2;
  string email = 3;
}

message ListUsersRequest {}
message ListUsersResponse {
  repeated User users = 1;
}

Go gRPC Server:

type server struct {
    pb.UnimplementedUserServiceServer
}

func (s *server) GetUser(ctx context.Context, req *pb.GetUserRequest) (*pb.GetUserResponse, error) {
    // Database lookup logic
    return &pb.GetUserResponse{
        Id:    req.Id,
        Name:  "John Doe",
        Email: "john@example.com",
    }, nil
}

func main() {
    lis, err := net.Listen("tcp", ":50051")
    if err != nil {
        log.Fatalf("Failed to listen: %v", err)
    }

    s := grpc.NewServer()
    pb.RegisterUserServiceServer(s, &server{})
    
    log.Println("gRPC server listening on :50051")
    if err := s.Serve(lis); err != nil {
        log.Fatalf("Failed to serve: %v", err)
    }
}

Advanced Concurrency Patterns

Fan-Out/Fan-In:

func fanIn(input1, input2 <-chan string) <-chan string {
    output := make(chan string)
    
    go func() {
        defer close(output)
        for {
            select {
            case s := <-input1:
                output <- s
            case s := <-input2:
                output <- s
            case <-time.After(time.Second):
                return
            }
        }
    }()
    
    return output
}

func main() {
    ch1 := make(chan string)
    ch2 := make(chan string)
    
    // Send data to channels
    go func() {
        for i := 0; i < 5; i++ {
            ch1 <- fmt.Sprintf("Channel 1: %d", i)
            time.Sleep(100 * time.Millisecond)
        }
        close(ch1)
    }()
    
    go func() {
        for i := 0; i < 5; i++ {
            ch2 <- fmt.Sprintf("Channel 2: %d", i)
            time.Sleep(150 * time.Millisecond)
        }
        close(ch2)
    }()
    
    // Receive from combined channel
    for msg := range fanIn(ch1, ch2) {
        fmt.Println(msg)
    }
}

Testing with Testify

import (
    "github.com/stretchr/testify/assert"
    "github.com/stretchr/testify/mock"
    "github.com/stretchr/testify/suite"
)

type UserTestSuite struct {
    suite.Suite
    user *User
}

func (suite *UserTestSuite) SetupTest() {
    suite.user = &User{ID: 1, Name: "John", Email: "john@example.com"}
}

func (suite *UserTestSuite) TestUserCreation() {
    assert.Equal(suite.T(), 1, suite.user.ID)
    assert.Equal(suite.T(), "John", suite.user.Name)
    assert.Equal(suite.T(), "john@example.com", suite.user.Email)
}

func TestUserTestSuite(t *testing.T) {
    suite.Run(t, new(UserTestSuite))
}

Level 4: Production Deployment

Production Best Practices

1. Use context for timeouts in concurrent operations
2. Handle errors immediately with meaningful messages
3. Use type-safe SQL with sqlc, not raw queries
4. Implement connection pooling for databases
5. Use middleware for cross-cutting concerns (logging, auth)
6. Goroutines should be bounded to prevent resource exhaustion
7. Close channels explicitly to signal completion
8. Use sync.WaitGroup for goroutine synchronization
9. Profile before optimization with pprof
10. Deploy with graceful shutdown handling

Docker Deployment

FROM golang:1.25-alpine AS builder
WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -o main .

FROM alpine:latest
RUN apk --no-cache add ca-certificates
WORKDIR /root/
COPY --from=builder /app/main .
EXPOSE 3000
CMD ["./main"]

Graceful Shutdown

func main() {
    app := fiber.New()
    
    // Setup routes...
    
    // Graceful shutdown
    ctx, cancel := context.WithCancel(context.Background())
    
    go func() {
        sigchan := make(chan os.Signal, 1)
        signal.Notify(sigchan, os.Interrupt)
        <-sigchan
        cancel()
    }()
    
    go func() {
        <-ctx.Done()
        log.Println("Shutting down server...")
        app.Shutdown()
    }()
    
    app.Listen(":3000")
}

Related Skills

• Skill("moai-domain-cli-tool") for CLI development
• Skill("moai-essentials-perf") for performance optimization
• Skill("moai-security-backend") for security patterns

Version: 4.0.0 Enterprise
Last Updated: 2025-11-13
Status: Production Ready