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====== GOLANG CODING CONVENTION ======

This document defines the coding conventions for projects written in Go (Golang).

===== Goals =====

  * Improve readability and maintainability of the codebase
  * Ensure a consistent coding style across the team
  * Reduce friction in code reviews and onboarding
  * Leverage Go’s ecosystem and tools effectively

These conventions apply to all Go code in this repository unless explicitly stated otherwise.

===== Table of Contents =====

  * [[#general_principles|1. General Principles]]
  * [[#naming_conventions|2. Naming Conventions]]
    * [[#package_names|2.1 Package Names]]
    * [[#variables_functions_and_methods|2.2 Variables, Functions, and Methods]]
    * [[#structs_interfaces_and_exported_symbols|2.3 Structs, Interfaces, and Exported Symbols]]
    * [[#constants_and_acronyms|2.4 Constants and Acronyms]]
    * [[#general_naming_guidelines|2.5 General Naming Guidelines]]
  * [[#formatting|3. Formatting]]
  * [[#project_structure|4. Project Structure]]
  * [[#functions_and_methods|5. Functions and Methods]]
  * [[#error_handling|6. Error Handling]]
  * [[#comments_and_documentation|7. Comments and Documentation]]
  * [[#configuration_context_and_logging|8. Configuration, Context, and Logging]]
  * [[#batch_coding|9. Batch Coding]]
  * [[#testing|10. Testing]]
  * [[#tools_and_static_analysis|11. Tools and Static Analysis]]

===== 1. General Principles =====
<anchor general_principles />

  * Prefer clarity over cleverness
  * Keep functions, types, and packages small and focused
  * Follow idiomatic Go practices

References:
  * [[https://golang.org/doc/effective_go.html|Effective Go]]
  * [[https://go.dev/wiki/CodeReviewComments|Go Code Review Comments]]
  * Go standard library (fmt, net/http, context, time, strings, errors, io, etc.)

When in doubt, idiomatic Go style takes precedence over personal preference.

===== 2. Naming Conventions =====

Identifiers starting with an uppercase letter are **exported**.  
Identifiers starting with a lowercase letter are **unexported**.

==== 2.1 Package Names ====

  * Use lowercase names
  * Do not use CamelCase
  * Avoid underscores unless absolutely necessary

Examples:
  * ``package user``
  * ``package auth``
  * ``package config``

File naming examples:
  * ``user_service.go``
  * ``user_repository.go``
  * ``http_handler.go``

==== 2.2 Variables, Functions, and Methods ====

Use **camelCase** for unexported identifiers.

<code go>
var maxRetries = 3

func newUserRepo(db *sql.DB) *userRepo {
    return &userRepo{db: db}
}

type userRepo struct {
    db *sql.DB
}
</code>

==== 2.3 Structs, Interfaces, and Exported Symbols ====

Use **PascalCase** for exported identifiers.

<code go>
type UserService struct {
    Repo UserRepository
}

func NewUserService(repo UserRepository) *UserService {
    return &UserService{Repo: repo}
}

type UserRepository interface {
    FindByID(ctx context.Context, id string) (*User, error)
}
</code>

==== 2.4 Constants and Acronyms ====

Constants typically use PascalCase.

<code go>
const (
    DefaultTimeout = 30 * time.Second
    HTTPTimeout    = 10 * time.Second
    MaxRetries     = 3
)
</code>

Common acronyms should be all caps.

<code go>
type HTTPServer struct{}
type UserID string

func NewJSONEncoder() JSONEncoder {}

const HTTPTimeout = 10 * time.Second
</code>

==== 2.5 General Naming Guidelines ====

; Types
: Should be nouns or noun phrases  
: Examples: ``User``, ``Order``, ``UserService``

; Functions and methods
: Should be verbs or verb phrases  
: Examples: ``CreateUser``, ``ValidateToken``

; Interfaces
: Should, where appropriate, end with ``-er``  
: Examples: ``Reader``, ``Writer``, ``UserRepository``

; Short-lived or small scopes
: Used in loops or short blocks  
: Examples: ``i``, ``j``, ``n``, ``err``

; Longer-lived or wider scopes
: Should use meaningful names  
: Examples: ``userID``, ``ctx``, ``cfg``

===== 3. Formatting =====

  * Always format code using ``gofmt`` or ``goimports``
  * Tabs are used for indentation
  * Opening braces must be on the same line

<code go>
if condition {
    // ...
}
</code>

Import grouping example:

<code go>
import (
    "context"
    "fmt"
    "net/http"

    "github.com/yourorg/yourproject/internal/user"
)
</code>

===== 4. Project Structure =====

<code>
.
├── cmd/
│   └── appname/
│       └── main.go
├── internal/
│   ├── domain/
│   ├── infrastructure/
│   ├── presentation/
│   ├── config/
│   ├── constant/
│   ├── validator/
├── pkg/
├── configs/
└── go.mod
</code>

Guidelines:
  * ``cmd``: application entry points and wiring
  * ``internal``: non-public application code
  * ``pkg``: reusable libraries (if needed)

===== 5. Functions and Methods =====

  * Functions should have a single responsibility
  * Avoid very long functions (over ~100 lines)
  * Prefer no more than 3 parameters

Options struct example:

<code go>
type CreateUserOptions struct {
    Name  string
    Email string
    Role  string
}

func (s *UserService) CreateUser(
    ctx context.Context,
    opts CreateUserOptions,
) (*User, error) {
    // ...
}
</code>

Prefer early returns:

<code go>
if err != nil {
    return nil, err
}
</code>

===== 6. Error Handling =====

Always handle errors immediately.

<code go>
user, err := s.repo.FindByID(ctx, id)
if err != nil {
    return nil, err
}
</code>

Use ``errors.Is`` and ``errors.As``:

<code go>
if errors.Is(err, sql.ErrNoRows) {
    return nil, ErrUserNotFound
}
</code>

Error message rules:
  * Start with a lowercase letter
  * Do not end with a period
  * Be short and descriptive

<code go>
return fmt.Errorf("failed to save user: %w", err)
</code>

===== 7. Comments and Documentation =====

==== 7.1 Doc Comments ====

Every exported identifier must have a doc comment.

<code go>
// UserService handles user-related operations.
type UserService struct {}
</code>

==== 7.2 Comment the Why ====

Avoid comments that repeat code behavior.

Bad:
<code go>
// Increase increases the counter by 1.
func (c *Counter) Increase() { c.value++ }
</code>

Good:
<code go>
// Increase increments the counter safely for concurrent use.
func (c *Counter) Increase() {}
</code>

===== 8. Configuration, Context and Logging =====

==== 8.1 Configuration ====

Centralize configuration loading and validation in ``internal/config``.

==== 8.2 context.Context ====

Rules:
  * Must be the first parameter
  * Must not be stored in struct fields
  * Must never be nil

<code go>
func (s *UserService) GetByID(
    ctx context.Context,
    id string,
) (*User, error) {
    // ...
}
</code>

==== 8.3 Logging ====

Use ``log/slog`` for structured logging.

<code go>
slog.InfoContext(ctx, "user created", "user_id", userID)
slog.ErrorContext(ctx, "failed to create user", "error", err)
</code>

===== 9. Batch Coding =====

Batch jobs must implement:

<code go>
Run(ctx context.Context, args []string) error
</code>

Healthcheck example:

<code go>
type healthcheck struct{}

func (h *healthcheck) Run(ctx context.Context, args []string) error {
    slog.InfoContext(ctx, "OK")
    return nil
}
</code>

===== 10. Testing =====

  * Use the ``testing`` package
  * Prefer table-driven tests
  * Use ``testify/assert`` for assertions
  * Use ``gomock`` for mocking
  * Suppress logs in tests

Dependency injection example:

<code go>
func NewPointAddUsecase(
    repo IAddPointRepository,
    crm IYappliCRMClient,
) *PointAddUsecase {
    return &PointAddUsecase{
        repo: repo,
        crm:  crm,
    }
}
</code>

===== 11. Tools and Static Analysis =====

==== 11.1 gofmt ====

<code sh>
gofmt -w ./...
</code>

==== 11.2 goimports ====

Formats code and manages imports automatically.

==== 11.3 go vet ====

<code sh>
go vet ./...
</code>

==== 11.4 golangci-lint ====

Configured via ``.golangci.yml``.

<code yaml>
linters:
  enable:
    - govet
    - staticcheck
    - errcheck
</code>