Channel counter implementation in Go without using sync.WaitGroup nor sync.Mutex. Only channels.

counter.go

package main

import "sync/atomic"

func sum(counter *int32, i int32) *int32 {
	atomic.AddInt32(counter, i)
	return counter
}

func main() {
	var counter int32
	ch := make(chan *int32)
	for i := 0; i < 1000; i++ {
		go func(i int) {
			ch <- sum(&counter, int32(i))
		}(i)
	}

	for i := 0; i < 999; i++ {
		_ = <-ch
	}

	println(*(<-ch))
}