three.go

package main

import (
	"fmt"
	"time"

	"github.com/davecgh/go-spew/spew"
)

func main() {
	users := []User{
		{Name: "Al"},
		{Name: "John"},
		{Name: "Jack"},
	}

	for k, v := range users {
		v.SetID(k)
		go watcher(&v)
	}

	spew.Dump(users)
	time.Sleep(time.Hour)
}

func watcher(user *User) {
	for {
		time.Sleep(time.Second)
		fmt.Println(user.Name)
	}
}

type User struct {
	Name string
	ID   int
}

//
func (user *User) SetName(name string) {
	user.Name = name
}

func (user *User) SetID(id int) {
	user.ID = id
}