What does this print with GOMAXPROCS(1), and why?

package main

import (
	"fmt"
	"runtime"
	"sync"
)

func main() {
	runtime.GOMAXPROCS(1)
	var wg sync.WaitGroup
	for i := range 5 {
		wg.Add(1)
		go func() {
			defer wg.Done()
			fmt.Print(i, " ")
		}()
	}
	wg.Wait()
}

It usually prints 4 0 1 2 3. When a new goroutine is created, it goes into the P's runnext slot and pushes the previous occupant to the tail of the local queue. After the loop, runnext holds goroutine 4 and the queue holds 0–3. When main blocks in Wait, the scheduler runs runnext first.

Since Go 1.22, each loop iteration has its own i, so every goroutine prints a different value. (range 5 over an integer itself needs Go 1.22. With a classic for i := 0; i < 5; i++ loop under an older go directive, all five goroutines share one i and would all print 5.)

What the interviewer wants to hear: this order is an implementation detail and is not guaranteed. Race builds and future scheduler changes can alter it. If you need an order, enforce it with synchronization.