/go-naming

Variable Names

This reference provides detailed guidance on naming variables in Go, covering scope-based naming, single-letter conventions, and avoiding type redundancy.

Length Proportional to Scope

Advisory: Short names for small scopes, longer names for large scopes.

// Good - short scope, short name
for i := 0; i < len(items); i++ {
    process(items[i])
}

// Good - larger scope, clearer name
func processOrders(orders []*Order) error {
    pendingOrders := filterPending(orders)
    // ... 20+ lines of processing ...
    return nil
}

Single-Letter Variables

Advisory: Use single letters only when meaning is obvious.

Appropriate uses:

• Loop indices: i, j, k
• Coordinates: x, y, z
• Receivers: one or two letters
• Common types: r for io.Reader, w for io.Writer
• Short loops: for _, n := range nodes

// Good - familiar conventions
func Copy(w io.Writer, r io.Reader) (int64, error)

for i, v := range values {
    process(v)
}

// Bad - unclear single letters
func Process(a, b, c string) error  // what are a, b, c?

Avoid Type in Variable Name

Advisory: Don't include the type in the variable name.

When disambiguating multiple forms, use meaningful qualifiers:

// Good - meaningful distinction
limitRaw := r.FormValue("limit")
limit, err := strconv.Atoi(limitRaw)

// Also good
limitStr := r.FormValue("limit")
limit, err := strconv.Atoi(limitStr)

Prefix Unexported Globals with _

Source: Uber Go Style Guide

Prefix unexported top-level vars and consts with _ to clarify when they are used that they are global symbols.

Rationale: Top-level variables and constants have package scope. Using a generic name makes it easy to accidentally shadow the value in a different file.

// Bad - hard to distinguish from local variables
const (
    defaultPort = 8080
    defaultUser = "user"
)

func Bar() {
    defaultPort := 9090  // shadows global, no compile error
    fmt.Println("Default port", defaultPort)
}

// Good - clearly global
const (
    _defaultPort = 8080
    _defaultUser = "user"
)

Exception: Unexported error values use the err prefix without underscore:

var errUserNotFound = errors.New("user not found")
var errInvalidInput = errors.New("invalid input")