Unnamed Struct Type Method

main.go

package main

import (
	"fmt"
	"sync"
)

var cache = struct {
	sync.Mutex // Mutex is embedded so its methods are promoted to the unnamed struct type
	mapping map[string]string
}{
	mapping: make(map[string]string),
}

func Lookup(key string) (val string) {
	cache.Lock()
	val = cache.mapping[key]
	cache.Unlock()

	return
}

func main() {
	fmt.Println(Lookup("foo"))
}