The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Go Projects Workflow

Guidelines for working with Go projects using modern tooling.

Tool Grid

Task	Tool	Command
Lint	golangci-lint	golangci-lint run
Format	goimports	goimports -w .
Build	go build	go build ./...
Test	go test	go test ./...
Coverage	go test	go test -cover ./...
Fuzzing	native	go test -fuzz=Fuzz
Race detection	built-in	go test -race ./...
Vulnerability	govulncheck	govulncheck ./...

---

Go Modules

go.mod Management

• You MUST use Go modules for all new projects
• You SHOULD run go mod tidy after adding or removing dependencies
• You MUST NOT commit a go.mod with replace directives unless for local development
• You SHOULD use exact version pinning for critical dependencies

// Good: explicit version
require github.com/pkg/errors v0.9.1

// Avoid: pseudo-versions when tagged releases exist
require github.com/pkg/errors v0.0.0-20210101000000-abcdef123456

go.sum Handling

• You MUST commit go.sum to version control
• You SHOULD NOT manually edit go.sum
• Run go mod verify to check integrity

Dependency Updates

# Update all dependencies
go get -u ./...

# Update specific dependency
go get -u github.com/pkg/errors

# Update to specific version
go get github.com/pkg/errors@v0.9.1

# Remove unused dependencies
go mod tidy

---

Error Handling

Error Wrapping

• You MUST wrap errors with context using fmt.Errorf and %w
• You SHOULD include the operation that failed in the error message

// Good: wrapped with context
if err != nil {
    return fmt.Errorf("failed to open config file %s: %w", path, err)
}

// Bad: loses error chain
if err != nil {
    return fmt.Errorf("failed to open config: %v", path)
}

Custom Error Types

• You SHOULD define custom error types for domain-specific errors
• You MUST implement the error interface

type NotFoundError struct {
    Resource string
    ID       string
}

func (e *NotFoundError) Error() string {
    return fmt.Sprintf("%s with ID %s not found", e.Resource, e.ID)
}

Error Checking

• You MUST use errors.Is() for sentinel error comparison
• You MUST use errors.As() for type assertion on errors

// Good: unwraps error chain
if errors.Is(err, os.ErrNotExist) {
    // handle missing file
}

// Good: extract typed error
var notFound *NotFoundError
if errors.As(err, &notFound) {
    // handle not found
}

// Bad: direct comparison (breaks with wrapping)
if err == os.ErrNotExist {
    // may not match wrapped errors
}

Sentinel Errors

• You SHOULD define sentinel errors as package-level variables
• You MUST use errors.New() for simple sentinel errors

var (
    ErrNotFound     = errors.New("resource not found")
    ErrUnauthorized = errors.New("unauthorized access")
)

---

Context Propagation

Function Signatures

• You MUST pass context.Context as the first parameter
• You MUST name the parameter ctx

// Good
func FetchUser(ctx context.Context, id string) (*User, error) {
    // ...
}

// Bad: context not first
func FetchUser(id string, ctx context.Context) (*User, error) {
    // ...
}

Context Usage

• You MUST NOT store context in structs
• You SHOULD check for context cancellation in long-running operations
• You SHOULD use context.WithTimeout or context.WithDeadline for operations with time limits

func ProcessItems(ctx context.Context, items []Item) error {
    for _, item := range items {
        select {
        case <-ctx.Done():
            return ctx.Err()
        default:
            if err := process(ctx, item); err != nil {
                return err
            }
        }
    }
    return nil
}

Context Values

• You SHOULD avoid using context.WithValue for passing optional parameters
• Context values SHOULD only be used for request-scoped data (trace IDs, auth tokens)
• You MUST use typed keys to avoid collisions

type contextKey string

const userIDKey contextKey = "userID"

func WithUserID(ctx context.Context, id string) context.Context {
    return context.WithValue(ctx, userIDKey, id)
}

func UserIDFromContext(ctx context.Context) (string, bool) {
    id, ok := ctx.Value(userIDKey).(string)
    return id, ok
}

---

Concurrency Patterns

Goroutines

• You MUST NOT start goroutines without a way to stop them
• You SHOULD use sync.WaitGroup to wait for goroutines to complete
• You MUST handle panics in goroutines

func ProcessConcurrently(ctx context.Context, items []Item) error {
    var wg sync.WaitGroup
    errCh := make(chan error, len(items))

    for _, item := range items {
        wg.Add(1)
        go func(item Item) {
            defer wg.Done()
            defer func() {
                if r := recover(); r != nil {
                    errCh <- fmt.Errorf("panic: %v", r)
                }
            }()
            if err := process(ctx, item); err != nil {
                errCh <- err
            }
        }(item)
    }

    wg.Wait()
    close(errCh)

    for err := range errCh {
        if err != nil {
            return err
        }
    }
    return nil
}

Channels

• You SHOULD prefer channels for communication between goroutines
• You MUST close channels from the sender side only
• You SHOULD use buffered channels when the number of items is known

// Good: producer closes channel
func Generate(ctx context.Context, n int) <-chan int {
    ch := make(chan int)
    go func() {
        defer close(ch)
        for i := 0; i < n; i++ {
            select {
            case <-ctx.Done():
                return
            case ch <- i:
            }
        }
    }()
    return ch
}

Sync Package

• You SHOULD use sync.Mutex for protecting shared state
• You SHOULD use sync.RWMutex when reads significantly outnumber writes
• You SHOULD use sync.Once for one-time initialization

type Cache struct {
    mu    sync.RWMutex
    items map[string]Item
}

func (c *Cache) Get(key string) (Item, bool) {
    c.mu.RLock()
    defer c.mu.RUnlock()
    item, ok := c.items[key]
    return item, ok
}

func (c *Cache) Set(key string, item Item) {
    c.mu.Lock()
    defer c.mu.Unlock()
    c.items[key] = item
}

---

Testing

Table-Driven Tests

• You SHOULD use table-driven tests for testing multiple cases

func TestAdd(t *testing.T) {
    tests := []struct {
        name     string
        a, b     int
        expected int
    }{
        {"positive numbers", 2, 3, 5},
        {"negative numbers", -1, -2, -3},
        {"zero", 0, 0, 0},
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            result := Add(tt.a, tt.b)
            if result != tt.expected {
                t.Errorf("Add(%d, %d) = %d; want %d", tt.a, tt.b, result, tt.expected)
            }
        })
    }
}

Test Fixtures

• You SHOULD place test data in a testdata/ directory
• The testdata/ directory is ignored by the Go toolchain

func TestParseConfig(t *testing.T) {
    data, err := os.ReadFile("testdata/config.json")
    if err != nil {
        t.Fatal(err)
    }
    // use data...
}

Test Helpers

• You SHOULD use t.Helper() in test helper functions
• Helper functions SHOULD take testing.TB to work with both tests and benchmarks

func assertNoError(t testing.TB, err error) {
    t.Helper()
    if err != nil {
        t.Fatalf("unexpected error: %v", err)
    }
}

Race Detection

• You MUST run tests with -race flag in CI
• You SHOULD run go test -race ./... locally before pushing

# CI configuration
go test -race -coverprofile=coverage.out ./...

---

Project Structure

Standard Layout

myproject/
├── cmd/                    # Main applications
│   └── myapp/
│       └── main.go
├── internal/               # Private application code
│   ├── config/
│   ├── handlers/
│   └── service/
├── pkg/                    # Public library code
│   └── client/
├── api/                    # API definitions (OpenAPI, proto)
├── web/                    # Web assets
├── scripts/                # Build and CI scripts
├── testdata/               # Test fixtures
├── go.mod
├── go.sum
└── Makefile

Package Organization

• cmd/ SHOULD contain only main packages with minimal logic
• internal/ MUST contain code that SHOULD NOT be imported by other projects
• pkg/ MAY contain code intended for external use
• You SHOULD avoid deeply nested package structures

Main Package

• The main package SHOULD be minimal
• You SHOULD move business logic to internal packages

// cmd/myapp/main.go
package main

import (
    "log"
    "os"

    "myproject/internal/app"
)

func main() {
    if err := app.Run(os.Args[1:]); err != nil {
        log.Fatal(err)
    }
}

---

Naming Conventions

General Rules

• You MUST use MixedCaps (PascalCase for exported, camelCase for unexported)
• You MUST NOT use underscores in Go names
• You SHOULD use short names for local variables with small scope

// Good
func ProcessUsers(users []User) error {
    for i, u := range users {
        // short names ok for loop variables
    }
}

// Bad
func ProcessUsers(users []User) error {
    for index, user := range users {
        // unnecessarily verbose
    }
}

Package Names

• Package names MUST be lowercase, single-word
• You MUST NOT use underscores or mixedCaps
• Package name SHOULD NOT repeat the import path

// Good
package http

// Bad
package httpClient
package http_client

Interface Names

• Single-method interfaces SHOULD end in -er suffix
• You SHOULD NOT prefix interface names with "I"

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

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

// Bad
type IUserService interface {
    GetUser(ctx context.Context, id string) (*User, error)
}

Acronyms

• Acronyms SHOULD be all caps or all lowercase
• You MUST be consistent within a project

// Good
var httpClient *http.Client
var HTTPClient *http.Client  // exported
var userID string
var UserID string            // exported

// Bad
var HttpClient *http.Client
var userId string

---

Interface Design

Accept Interfaces, Return Structs

• Function parameters SHOULD accept interfaces when possible
• Functions SHOULD return concrete types

// Good: accepts interface
func ProcessData(r io.Reader) error {
    // can accept any Reader
}

// Good: returns concrete type
func NewService(db *sql.DB) *Service {
    return &Service{db: db}
}

// Bad: returns interface (unless abstracting implementations)
func NewService(db *sql.DB) ServiceInterface {
    return &Service{db: db}
}

Small Interfaces

• You SHOULD define small, focused interfaces
• You SHOULD compose larger interfaces from smaller ones

// Good: small, focused interfaces
type Reader interface {
    Read(p []byte) (n int, err error)
}

type Writer interface {
    Write(p []byte) (n int, err error)
}

type ReadWriter interface {
    Reader
    Writer
}

Interface Location

• Interfaces SHOULD be defined where they are used, not where they are implemented
• This allows consumers to define only what they need

// In consumer package
type UserGetter interface {
    GetUser(ctx context.Context, id string) (*User, error)
}

// Service implementation doesn't need to know about this interface
func NewHandler(users UserGetter) *Handler {
    return &Handler{users: users}
}

---

Common Patterns

Functional Options

• You SHOULD use functional options for configurable constructors

type Server struct {
    addr    string
    timeout time.Duration
}

type Option func(*Server)

func WithTimeout(d time.Duration) Option {
    return func(s *Server) {
        s.timeout = d
    }
}

func NewServer(addr string, opts ...Option) *Server {
    s := &Server{
        addr:    addr,
        timeout: 30 * time.Second, // default
    }
    for _, opt := range opts {
        opt(s)
    }
    return s
}

Graceful Shutdown

• You MUST handle OS signals for graceful shutdown
• You SHOULD use context for coordinating shutdown

func main() {
    ctx, cancel := signal.NotifyContext(context.Background(),
        syscall.SIGINT, syscall.SIGTERM)
    defer cancel()

    srv := &http.Server{Addr: ":8080"}

    go func() {
        <-ctx.Done()
        shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
        defer cancel()
        srv.Shutdown(shutdownCtx)
    }()

    if err := srv.ListenAndServe(); err != http.ErrServerClosed {
        log.Fatal(err)
    }
}

---

CI/CD Requirements

Required Checks

• You MUST run go build ./... to verify compilation
• You MUST run go test -race ./... for race detection
• You SHOULD run golangci-lint run for static analysis
• You SHOULD run govulncheck ./... for vulnerability scanning

Example GitHub Actions

name: Go
on: [push, pull_request]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-go@v5
        with:
          go-version: '1.22'
      - run: go build ./...
      - run: go test -race -coverprofile=coverage.out ./...
      - run: go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
      - run: golangci-lint run
      - run: go install golang.org/x/vuln/cmd/govulncheck@latest
      - run: govulncheck ./...