goAsync race conditionMedium

WaitGroup Add inside goroutine creates race condition

Time: 0:00

BugFind the bug and fix the code

What it should do

Launch workers concurrently and wait for all to complete. Example: syncWorkerGroup(3) -> 3

What happens instead

wg.Wait() exits early before goroutines start, returning 0

package main

import (
	"fmt"
	"sync"
)

func syncWorkerGroup(count int) int {
	var wg sync.WaitGroup
	completed := 0
	for i := 0; i < count; i++ {
		go func() {
			wg.Add(1)
			defer wg.Done()
			completed++
		}()
	}
	wg.Wait()
	return completed
}

func main() {
	fmt.Println(syncWorkerGroup(3))
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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This bug belongs to the async and race conditions pattern

A missing await, unbuffered channel deadlocks, ConcurrentModificationException, and data races under load.

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package main import ( "fmt" "sync" ) func syncWorkerGroup(count int) int { var wg sync.WaitGroup completed := 0 for i := 0; i < count; i++ { go func() { wg.Add(1) defer wg.Done() completed++ }() } wg.Wait() return completed } func main() { fmt.Println(syncWorkerGroup(3)) }

WaitGroup Add inside goroutine creates race condition

What it should do

What happens instead

More async and race conditions to practise

WaitGroup Add inside goroutine creates race condition

What it should do

What happens instead

More async and race conditions to practise