go - Unexpected behavior from launching a method call on a loop variable as a goroutine

Question

I read this article and decided to repeat such behavior myself and experiment with that:

package main

import (
    "fmt"
    "time"
)

type User struct {
    i    int
    token string
}

func NewUser(i int, token string) User {
    user := User{token: fmt.Sprint(i), i: i}
    return user
}

func (u *User) PrintAddr() {
    fmt.Printf("%d (PrintAddr): %p
", u.i, u)
}

func main() {
    users := make([]User, 4)
    for i := 0; i < 4; i++ {
        user := NewUser(i, "")
        users[i] = user
    }
    
    for i, user := range users {
        go user.PrintAddr()
        go users[i].PrintAddr()
    }
    time.Sleep(time.Second)
}

(Playground)

Here is the code output:

1 (PrintAddr): 0xc000056198
2 (PrintAddr): 0xc0000561b0
0 (PrintAddr): 0xc000056180
3 (PrintAddr): 0xc00000c030
3 (PrintAddr): 0xc00000c030
3 (PrintAddr): 0xc00000c030
3 (PrintAddr): 0xc00000c030
3 (PrintAddr): 0xc0000561c8

I also don't understand, why are 4 of 5 3 (PrintAddr) are 0xc00000c030, and the last one is different?

---

However, if I use a pointer array instead of value array, like this,

func NewUser(i int, token string) *User {
    user := &User{token: fmt.Sprint(i), i: i}
    return user
}
// -snip-
func main() {
    users := make([]*User, 4)
    // -snip-

(Playground)

then everything's fine here and each entry is printed exactly 2 times with the same address:

1 (PrintAddr): 0xc0000ae030
3 (PrintAddr): 0xc0000ae060
2 (PrintAddr): 0xc0000ae048
2 (PrintAddr): 0xc0000ae048
3 (PrintAddr): 0xc0000ae060
1 (PrintAddr): 0xc0000ae030
0 (PrintAddr): 0xc0000ae018
0 (PrintAddr): 0xc0000ae018

But why did the situation in the article not apply here and I didn't get many 3 (PrintAddr) instead?

Answer 1

Waitting for answers