Go -

Generators

Thread safe unique ID generator.

package main

import "fmt"

func getIdGenerator() chan string {
    c := make(chan string)
    go func() {
        var nextId int64 = 0
        for {
            c <- fmt.Sprintf("%x", nextId)
            nextId += 1
        }
    }()
    return c
}

func main() {
    idGenerator1 := getIdGenerator()
    fmt.Println(<-idGenerator1) // 0
    fmt.Println(<-idGenerator1) // 1
    fmt.Println(<-idGenerator1) // 2
    idGenerator2 := getIdGenerator()
    idGenerator3 := getIdGenerator()
    fmt.Println(<-idGenerator1) // 3
    fmt.Println(<-idGenerator2) // 0
    fmt.Println(<-idGenerator3) // 0
}