Use atomic Int32 instead of Bool

Small change that lets us keep Go 1.15 support

udp/batchconn.go

@@ -47,7 +47,7 @@ type BatchConn struct {
 	batchWriteSize     int
 	batchWriteInterval time.Duration
 
-	closed atomic.Bool
+	closed int32
 }
 
 // NewBatchConn creates a *BatchConn from net.PacketConn with batch configs.
@@ -76,8 +76,7 @@ func NewBatchConn(conn net.PacketConn, batchWriteSize int, batchWriteInterval ti
 		go func() {
 			writeTicker := time.NewTicker(batchWriteInterval / 2)
 			defer writeTicker.Stop()
-
-			for !bc.closed.Load() {
+			for atomic.LoadInt32(&bc.closed) != 1 {
 				<-writeTicker.C
 				bc.batchWriteMutex.Lock()
 				if bc.batchWritePos > 0 && time.Since(bc.batchWriteLast) >= bc.batchWriteInterval {
@@ -93,7 +92,7 @@ func NewBatchConn(conn net.PacketConn, batchWriteSize int, batchWriteInterval ti
 
 // Close batchConn and the underlying PacketConn
 func (c *BatchConn) Close() error {
-	c.closed.Store(true)
+	atomic.StoreInt32(&c.closed, 1)
 	c.batchWriteMutex.Lock()
 	if c.batchWritePos > 0 {
 		_ = c.flush()

udp/conn_test.go

@@ -502,10 +502,10 @@ func TestBatchIO(t *testing.T) {
 	var serverConnWg sync.WaitGroup
 	serverConnWg.Add(1)
 	go func() {
-		var exit atomic.Bool
+		var exit int32
 		defer func() {
 			defer serverConnWg.Done()
-			exit.Store(true)
+			atomic.StoreInt32(&exit, 1)
 		}()
 		for {
 			buf := make([]byte, 1400)
@@ -520,7 +520,7 @@ func TestBatchIO(t *testing.T) {
 					_ = conn.Close()
 					serverConnWg.Done()
 				}()
-				for !exit.Load() {
+				for atomic.LoadInt32(&exit) != 1 {
 					_ = conn.SetReadDeadline(time.Now().Add(time.Second))
 					n, rerr := conn.Read(buf)
 					if rerr != nil {