Go coding standards

Go Coding Standards

Idiomatic Go conventions grounded in Effective Go, Go Code Review Comments, and production-proven idioms. All code MUST pass goimports, golint, and go vet without errors.

1. Import Ordering

Group imports in this order, separated by blank lines:

import (
    // 1. Standard library
    "context"
    "fmt"
    "net/http"

    // 2. External packages
    "github.com/gorilla/mux"
    "log/slog"

    // 3. Internal/project packages
    "github.com/myorg/myproject/internal/service"
)

NEVER use dot imports. Use aliasing only to resolve conflicts.

2. Naming Conventions

Packages

• Short, lowercase, single-word names. No underscores, no camelCase.
• Name should describe what the package provides, not what it contains.
• Avoid generic names: util, common, helpers, misc, base.

Functions & Methods

• MixedCaps (exported) or mixedCaps (unexported). No underscores except in test files.
• Getters: use Name(), NOT GetName(). Setters: use SetName().
• Constructors: NewFoo() returns *Foo. If only one type in package: New().

Variables

• Short names in tight scopes: i, n, err, ctx.
• Descriptive names for wider scopes: userCount, retryTimeout.
• Prefix unexported package-level globals with _: var _defaultTimeout = 5 * time.Second.
• Do NOT shadow built-in identifiers (error, len, cap, new, make, close).

Interfaces

• Single-method interfaces: method name + -er suffix (Reader, Writer, Closer).
• Define interfaces where they are consumed, not where they are implemented.

3. Variable Declarations

Top-level

Use var for top-level declarations. Do NOT specify type when it matches the expression:

// ✅ Good
var _defaultPort = 8080
var _logger = slog.Default()

// ❌ Bad — redundant type
var _defaultPort int = 8080

Local

• Prefer := for local variables.
• Use var only when zero-value initialization is intentional and meaningful.

// ✅ Good — zero value is meaningful
var buf bytes.Buffer

// ✅ Good — short declaration
name := getUserName()

4. Struct Initialization

ALWAYS use field names. Never rely on positional initialization:

// ✅ Good
user := User{
    Name:  "Alice",
    Email: "[email protected]",
    Age:   30,
}

// ❌ Bad — positional, breaks on field reordering
user := User{"Alice", "[email protected]", 30}

Omit zero-value fields unless clarity requires them:

// ✅ Good — zero values omitted
user := User{
    Name: "Alice",
}

5. Reduce Nesting

Handle errors and special cases first with early returns. Reduce indentation levels:

// ✅ Good — early return
func process(data []Item) error {
    for _, v := range data {
        if !v.IsValid() {
            log.Printf("invalid item: %v", v)
            continue
        }

        if err := v.Process(); err != nil {
            return err
        }

        v.Send()
    }
    return nil
}

Eliminate unnecessary else blocks:

// ✅ Good
a := 10
if condition {
    a = 20
}

// ❌ Bad
var a int
if condition {
    a = 20
} else {
    a = 10
}

6. Grouping and Ordering

Group related declarations:

const (
    _defaultPort    = 8080
    _defaultTimeout = 30 * time.Second
)

var (
    _validTypes  = map[string]bool{"json": true, "xml": true}
    _defaultUser = User{Name: "guest"}
)

Function ordering within a file:

1. Constants and variables
2. New() / constructor functions
3. Exported methods (sorted by importance, not alphabetically)
4. Unexported methods
5. Helper functions

Receiver methods should appear immediately after the type declaration.

7. Line Length

Soft limit of 99 characters. Break long function signatures:

func (s *Store) CreateUser(
    ctx context.Context,
    name string,
    email string,
    opts ...CreateOption,
) (*User, error) {

8. Defer Usage

Use defer for cleanup. It makes intent clear at the point of acquisition:

mu.Lock()
defer mu.Unlock()

f, err := os.Open(path)
if err != nil {
    return err
}
defer f.Close()

9. Enums

Start enums at 1 (or use explicit sentinel) so zero-value signals "unset":

type Status int

const (
    StatusUnknown Status = iota
    StatusActive
    StatusInactive
)

10. Use time Package Properly

• Use time.Duration for durations, NOT raw integers.
• Use time.Time for instants. Use time.Since(start) instead of time.Now().Sub(start).
• External APIs: accept int or float64 and convert internally.

// ✅ Good
func poll(interval time.Duration) { ... }
poll(10 * time.Second)

// ❌ Bad
func poll(intervalSecs int) { ... }
poll(10)

Verification Checklist

Before considering code complete:

1. goimports runs clean
2. go vet ./... passes
3. golangci-lint run passes (if configured)
4. No shadowed built-in identifiers
5. All imports properly grouped and ordered
6. Struct initializations use field names
7. No unnecessary nesting or else blocks