fix: use atomic in retrier to prevent race conditions (#518)

Android/app/src/go/intra/split/retrier.go

@@ -23,6 +23,7 @@ import (
 	"math/rand"
 	"net"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/Jigsaw-Code/getsni"
@@ -62,8 +63,8 @@ type retrier struct {
 	// Flag indicating when retry is finished or unnecessary.
 	retryCompleteFlag chan struct{}
 	// Flags indicating whether the caller has called CloseRead and CloseWrite.
-	readCloseFlag  chan struct{}
-	writeCloseFlag chan struct{}
+	readCloseFlag  atomic.Bool
+	writeCloseFlag atomic.Bool
 	stats          *RetryStats
 }
 
@@ -87,11 +88,11 @@ func closed(c chan struct{}) bool {
 }
 
 func (r *retrier) readClosed() bool {
-	return closed(r.readCloseFlag)
+	return r.readCloseFlag.Load()
 }
 
 func (r *retrier) writeClosed() bool {
-	return closed(r.writeCloseFlag)
+	return r.writeCloseFlag.Load()
 }
 
 func (r *retrier) retryCompleted() bool {
@@ -142,8 +143,6 @@ func DialWithSplitRetry(ctx context.Context, dialer *net.Dialer, addr *net.TCPAd
 		conn:              conn.(*net.TCPConn),
 		timeout:           timeout(before, after),
 		retryCompleteFlag: make(chan struct{}),
-		readCloseFlag:     make(chan struct{}),
-		writeCloseFlag:    make(chan struct{}),
 		stats:             stats,
 	}
 
@@ -211,9 +210,7 @@ func (r *retrier) retry(buf []byte) (n int, err error) {
 }
 
 func (r *retrier) CloseRead() error {
-	if !r.readClosed() {
-		close(r.readCloseFlag)
-	}
+	r.readCloseFlag.Store(true)
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
 	return r.conn.CloseRead()
@@ -363,9 +360,7 @@ func (r *retrier) ReadFrom(reader io.Reader) (bytes int64, err error) {
 }
 
 func (r *retrier) CloseWrite() error {
-	if !r.writeClosed() {
-		close(r.writeCloseFlag)
-	}
+	r.writeCloseFlag.Store(true)
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
 	return r.conn.CloseWrite()