go

Go: Idiomatic Efficiency Reference

When to Use

• Use this skill when the task matches this description: Language-specific super-code guidelines for go.

Table of Contents

1. [Error Handling](#errors)
2. [Slices & Maps](#slices)
3. [Goroutines & Channels](#concurrency)
4. [Structs & Interfaces](#structs)
5. [Functions & Closures](#functions)
6. [Anti-patterns specific to Go](#antipatterns)

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1. Error Handling {#errors}

// ❌ Ignoring errors
result, _ := os.Open(path)

// ✅ — always handle; only use _ when error is provably irrelevant
result, err := os.Open(path)
if err != nil {
    return fmt.Errorf("open %s: %w", path, err)
}

// ❌ Redundant error variable
err := doA()
if err != nil { return err }
err = doB()
if err != nil { return err }

// ✅ — each :=/:  is fine; this is idiomatic Go. Don't try to "fix" it.
// What you CAN simplify: collapsing to one-liners where the if body is a single return
if err := doA(); err != nil { return err }
if err := doB(); err != nil { return err }

// ❌ Custom error type with no added value
type MyError struct{ msg string }
func (e MyError) Error() string { return e.msg }

// ✅ — use errors.New or fmt.Errorf unless callers need to inspect type
var ErrNotFound = errors.New("not found")
return fmt.Errorf("lookup %q: %w", key, ErrNotFound)

**Wrap errors with %w (not %v) so callers can use `errors.I