go-database

# Go Database Skill

Production database patterns with Go including SQL, ORMs, and data access layer design.

## Overview

Best practices for database operations covering connection pooling, transactions, migrations, and query optimization.

## Parameters

| Parameter | Type | Required | Default | Description |
|-----------|------|----------|---------|-------------|
| database | string | yes | - | Database: "postgres", "mysql", "sqlite" |
| orm | string | no | "sqlx" | ORM: "none", "sqlx", "gorm" |
| pool_size | int | no | 25 | Max open connections |

## Core Topics

### Connection Setup
```go
func NewDB(dsn string) (*sqlx.DB, error) {
    db, err := sqlx.Connect("postgres", dsn)
    if err != nil {
        return nil, fmt.Errorf("connect: %w", err)
    }

    db.SetMaxOpenConns(25)
    db.SetMaxIdleConns(5)
    db.SetConnMaxLifetime(5 * time.Minute)
    db.SetConnMaxIdleTime(1 * time.Minute)

    if err := db.Ping(); err != nil {
        return nil, fmt.Errorf("ping: %w", err)
    }

    return db, nil
}
```

### Repository Pattern
```go
type UserRepository struct {
    db *sqlx.DB
}

func (r *UserRepository) FindByID(ctx context.Context, id int64) (*User, error) {
    var user User
    err := r.db.GetContext(ctx, &user,
        `SELECT id, name, email, created_at FROM users WHERE id = $1`, id)
    if err != nil {
        if errors.Is(err, sql.ErrNoRows) {
            return nil, ErrUserNotFound
        }
        return nil, fmt.Errorf("find user %d: %w", id, err)
    }
    return &user, nil
}

func (r *UserRepository) Create(ctx context.Context, user *User) error {
    query := `INSERT INTO users (name, email) VALUES ($1, $2) RETURNING id, created_at`
    return r.db.QueryRowxContext(ctx, query, user.Name, user.Email).
        Scan(&user.ID, &user.CreatedAt)
}
```

### Transactions
```go
func (r *OrderRepository) CreateOrder(ctx context.Context, order *Order, items []OrderItem) error {
    tx, err := r.db.BeginTxx(ctx, nil)
    if err != nil {
        return fmt.E