go routines mutex / published by https://github.com/dacr/code-examples-manager #e4bc0bea-e40e-4039-b5d1-e45d788d387e/f710e9e2878711664f63beb2323f792892ffd7c3

concurrency-goroutines-mutex.go

/*?sr/bin/true; exec /usr/bin/env nix-shell -p go --run "go run $0" #*/
// summary : go routines mutex
// keywords : go, goroutines, mutex, @testable
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : e4bc0bea-e40e-4039-b5d1-e45d788d387e
// created-on : 2025-03-27T15:17:01+01:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : nix-shell -p go --run "go run $file"
package main

import (
	"sync"
)

func main() {
	sg := sync.WaitGroup{}

	mutex := sync.Mutex{}
	list := []int{}

	for i := range 100 {
		sg.Add(1)
		go func() {
			defer sg.Done()
			mutex.Lock() // ************ to avoid concurrent access
			if len(list) < 20 {
				list = append(list, i)
			}
			mutex.Unlock() // ************
		}()
	}
	sg.Wait()
	for i, winner := range list {
		println(i, winner)
	}
}