Go 1 24

// No code changes required!
// All maps automatically use Swiss Tables
users := make(map[string]User)
users["alice"] = User{Name: "Alice"}

// Benefits:
// - Faster lookups (15-25%)
// - Faster insertions/updates (10-15%)
// - Faster deletions (10-15%)
// - Overall program: 2-3% faster

import "runtime"

type Resource struct {
    id   int
    file *os.File
}

func NewResource(id int, filename string) (*Resource, error) {
    file, err := os.Open(filename)
    if err != nil {
        return nil, err
    }

    r := &Resource{id: id, file: file}

    // Attach cleanup function
    runtime.AddCleanup(r, func(r *Resource) {
        fmt.Printf("Cleaning up resource %d\n", r.id)
        r.file.Close()
    })

    return r, nil
}

// Open root directory for isolated operations
root, err := os.OpenRoot("/var/app/data")
if err != nil {
    log.Fatal(err)
}
defer root.Close()

// Open file (relative to root)
file, err := root.Open("config.json")

// Attempt path traversal
file, err = root.Open("../../etc/passwd")
// Error: Path escapes root directory

type SafeFileServer struct {
    root *os.Root
}

func (s *SafeFileServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    file, err := s.root.Open(path.Clean(r.URL.Path))
    if err != nil {
        http.Error(w, "File not found", http.StatusNotFound)
        return
    }
    defer file.Close()

    info, _ := file.Stat()
    http.ServeContent(w, r, info.Name(), info.ModTime(), file)
}

// Generic type alias
type Pair[T any] = struct {
    First  T
    Second T
}

p := Pair[int]{First: 1, Second: 2}

// Generic slice alias
type List[T any] = []T

numbers := List[int]{1, 2, 3}