diff --git a/once_test.go b/once_test.go
index 39d518d..7b99713 100644
--- a/once_test.go
+++ b/once_test.go
@@ -23,7 +23,7 @@ func TestOnce(t *testing.T) {
 
 func TestOnceConcurrent(t *testing.T) {
 	var once Once[int32]
-	var count int32
+	var count atomic.Int32
 	var wg sync.WaitGroup
 
 	for i := 0; i < 10; i++ {
@@ -31,14 +31,14 @@ func TestOnceConcurrent(t *testing.T) {
 		go func() {
 			defer wg.Done()
 			result, _ := once.Do(func() (int32, error) {
-				newCount := atomic.AddInt32(&count, 1)
+				newCount := count.Add(1)
 				return newCount, nil
 			})
-			atomic.StoreInt32(&count, result)
+			count.Store(result)
 		}()
 	}
 	wg.Wait()
-	assert.Equal(t, count, 1)
+	assert.Equal(t, int(count.Load()), 1)
 }
 
 func TestOncePanic(t *testing.T) {
diff --git a/wait_group_context.go b/wait_group_context.go
index 8880b3c..39a3743 100644
--- a/wait_group_context.go
+++ b/wait_group_context.go
@@ -13,8 +13,8 @@ import (
 type WaitGroupContext struct {
 	ctx     context.Context
 	done    chan struct{}
-	counter int32
-	state   int32
+	counter atomic.Int32
+	state   atomic.Int32
 }
 
 // NewWaitGroupContext returns a new WaitGroupContext with Context ctx.
@@ -29,10 +29,10 @@ func NewWaitGroupContext(ctx context.Context) *WaitGroupContext {
 // If the counter becomes zero, all goroutines blocked on Wait are released.
 // If the counter goes negative, Add panics.
 func (wgc *WaitGroupContext) Add(delta int) {
-	counter := atomic.AddInt32(&wgc.counter, int32(delta))
-	if counter == 0 && atomic.CompareAndSwapInt32(&wgc.state, 0, 1) {
+	counter := wgc.counter.Add(int32(delta))
+	if counter == 0 && wgc.state.CompareAndSwap(0, 1) {
 		wgc.release()
-	} else if counter < 0 && atomic.LoadInt32(&wgc.state) == 0 {
+	} else if counter < 0 && wgc.state.Load() == 0 {
 		panic("async: negative WaitGroupContext counter")
 	}
 }
diff --git a/wait_group_context_test.go b/wait_group_context_test.go
index 2b3b69e..f8de1eb 100644
--- a/wait_group_context_test.go
+++ b/wait_group_context_test.go
@@ -2,6 +2,7 @@ package async
 
 import (
 	"context"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -9,37 +10,37 @@ import (
 )
 
 func TestWaitGroupContext(t *testing.T) {
-	result := 0
+	var result atomic.Int32
 	wgc := NewWaitGroupContext(context.Background())
 	wgc.Add(2)
 
 	go func() {
 		defer wgc.Done()
 		time.Sleep(time.Millisecond * 10)
-		result++
+		result.Add(1)
 	}()
 	go func() {
 		defer wgc.Done()
 		time.Sleep(time.Millisecond * 20)
-		result += 2
+		result.Add(2)
 	}()
 	go func() {
 		wgc.Wait()
-		result += 3
+		result.Add(3)
 	}()
 
 	wgc.Wait()
 	time.Sleep(time.Millisecond * 10)
 
-	assert.Equal(t, result, 6)
+	assert.Equal(t, int(result.Load()), 6)
 }
 
 func TestWaitGroupContextCanceled(t *testing.T) {
-	result := 0
+	var result atomic.Int32
 	ctx, cancelFunc := context.WithCancel(context.Background())
 	go func() {
 		time.Sleep(time.Millisecond * 100)
-		result += 10
+		result.Add(10)
 		cancelFunc()
 	}()
 	wgc := NewWaitGroupContext(ctx)
@@ -48,22 +49,22 @@ func TestWaitGroupContextCanceled(t *testing.T) {
 	go func() {
 		defer wgc.Done()
 		time.Sleep(time.Millisecond * 10)
-		result++
+		result.Add(1)
 	}()
 	go func() {
 		defer wgc.Done()
 		time.Sleep(time.Millisecond * 300)
-		result += 2
+		result.Add(2)
 	}()
 	go func() {
 		wgc.Wait()
-		result += 100
+		result.Add(100)
 	}()
 
 	wgc.Wait()
 	time.Sleep(time.Millisecond * 10)
 
-	assert.Equal(t, result, 111)
+	assert.Equal(t, int(result.Load()), 111)
 }
 
 func TestWaitGroupContextPanic(t *testing.T) {