Fix data race

Author: wzshiming

tunnel.go

@@ -6,33 +6,24 @@ import (
 )
 
 func Tunnel(ctx context.Context, c1, c2 io.ReadWriteCloser, buf1, buf2 []byte) error {
-	ctx, cancel := context.WithCancel(ctx)
-	var errs tunnelErr
+	errCh := make(chan error, 2)
 	go func() {
-		_, errs[0] = io.CopyBuffer(c1, c2, buf1)
-		cancel()
+		_, err := io.CopyBuffer(c1, c2, buf1)
+		errCh <- err
 	}()
 	go func() {
-		_, errs[1] = io.CopyBuffer(c2, c1, buf2)
-		cancel()
+		_, err := io.CopyBuffer(c2, c1, buf2)
+		errCh <- err
+	}()
+	defer func() {
+		_ = c1.Close()
+		_ = c2.Close()
 	}()
-	<-ctx.Done()
-	errs[2] = c1.Close()
-	errs[3] = c2.Close()
-	errs[4] = ctx.Err()
-	if errs[4] == context.Canceled {
-		errs[4] = nil
-	}
-	return errs.FirstError()
-}
-
-type tunnelErr [5]error
 
-func (t tunnelErr) FirstError() error {
-	for _, err := range t {
-		if err != nil {
-			return err
-		}
+	select {
+	case err := <-errCh:
+		return err
+	case <-ctx.Done():
+		return ctx.Err()
 	}
-	return nil
 }