为什么在此golang代码段中，指向WaitGroup的指针的地址不同？

Question

Code snippet on playground

I am printing the pointer address for sync.WaitGroup and they are all different. Why?

func Run() *sync.WaitGroup {
    var wg sync.WaitGroup
    wg.Add(1)
    go func() {
        defer wg.Done()
        fmt.Printf("goroutine %p
", &wg)

        time.Sleep(5 * time.Second)
        fmt.Println("wokeup")
    }()

    fmt.Printf("returning %p
", &wg)
    return &wg
}

func main() {
    runtime.GOMAXPROCS(3)
    wg := Run()

    fmt.Printf("     main %p
", &wg)
    wg.Wait()
}

Typical output shows that the address is diff between that inside the function Run and main. I'd expect that to be the same, n'est-ce pas ?

returning 0xc0840045c0
     main 0xc084000038
goroutine 0xc0840045c0
wokeup

Answer 1

For example,

package main

import "fmt"
import "sync"
import "time"
import "runtime"

func Run() *sync.WaitGroup {
    var wg sync.WaitGroup
    wg.Add(1)
    go func() {
        defer wg.Done()
        fmt.Printf("goroutine %p
", &wg)
        fmt.Println("sleep for 5s")
        time.Sleep(5 * time.Second)
        fmt.Println("wokeup")
    }()
    fmt.Printf("returning %p
", &wg)
    return &wg
}

func main() {
    runtime.GOMAXPROCS(3)
    wg := Run()
    fmt.Printf("     main %p
", wg)
    wg.Wait()
}

Output:

returning 0x1052e2c0
     main 0x1052e2c0
goroutine 0x1052e2c0
sleep for 5s

Change

fmt.Printf("     main %p
", &wg)

to

fmt.Printf("     main %p
", wg)

In main, the variable wg contains the address you want. You are printing the address of the variable that contains the address.