goAsync race conditionHard

Unsafe atomic addition on raw float64 value

Time: 0:00

BugFind the bug and fix the code

What it should do

Concurrently add credit amount and return updated integer total. Example: atomicAddCredits(10, 5) -> 15

What happens instead

Non-atomic addition causes data race and inconsistent final balance

package main

import (
	"fmt"
	"sync"
)

func atomicAddCredits(initial int, delta int) int {
	total := initial
	var wg sync.WaitGroup
	// Mutating total across goroutines without sync
	wg.Add(1)
	go func() {
		defer wg.Done()
		total += delta
	}()
	wg.Wait()
	return total
}

func main() {
	fmt.Println(atomicAddCredits(10, 5))
}

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 atomicAddCredits(initial int, delta int) int { total := initial var wg sync.WaitGroup // Mutating total across goroutines without sync wg.Add(1) go func() { defer wg.Done() total += delta }() wg.Wait() return total } func main() { fmt.Println(atomicAddCredits(10, 5)) }

Unsafe atomic addition on raw float64 value

What it should do

What happens instead

More async and race conditions to practise

Unsafe atomic addition on raw float64 value

What it should do

What happens instead

More async and race conditions to practise