diff --git a/internal/netconn/multisplit_test.go b/internal/netconn/multisplit_test.go
index 8faeb7b..5bc965f 100644
--- a/internal/netconn/multisplit_test.go
+++ b/internal/netconn/multisplit_test.go
@@ -5,7 +5,7 @@ import (
 	"testing"
 )
 
-func u8(v int) byte { return byte(v) }
+func u8(v int) byte { return byte(v & 0xFF) }
 
 func buildClientHello(host string) []byte {
 	hn := []byte(host)
diff --git a/internal/proxy/udprelay/loop.go b/internal/proxy/udprelay/loop.go
index d4853ef..ebb4bb6 100644
--- a/internal/proxy/udprelay/loop.go
+++ b/internal/proxy/udprelay/loop.go
@@ -161,7 +161,8 @@ func oneDTLS(ctx context.Context, deps *Deps, params *Params, peer *net.UDPAddr,
 			if addr == nil {
 				continue
 			}
-			if _, err = listenConn.WriteTo(buf[:n], addr.(net.Addr)); err != nil {
+			_, writeErr := listenConn.WriteTo(buf[:n], addr.(net.Addr))
+			if writeErr != nil {
 				return
 			}
 		}
diff --git a/internal/session/session.go b/internal/session/session.go
index 6f9d59a..120941a 100644
--- a/internal/session/session.go
+++ b/internal/session/session.go
@@ -336,7 +336,7 @@ func (s *Session) relay(ctx context.Context, prov provider.Provider, peer *net.U
 		return err
 	}
 	if s.deps.LocalPipe == nil {
-		defer local.Close()
+		defer func() { _ = local.Close() }()
 	}
 
 	dialer := &dtlsdial.Dialer{
diff --git a/internal/tunnel/bind/bind_test.go b/internal/tunnel/bind/bind_test.go
index d05dac6..3f966d9 100644
--- a/internal/tunnel/bind/bind_test.go
+++ b/internal/tunnel/bind/bind_test.go
@@ -147,8 +147,8 @@ func TestSinglePeerBindReopenAfterClose(t *testing.T) {
 	}
 
 	in := []byte("response")
-	if _, err := relay.WriteTo(in, nil); err != nil {
-		t.Fatal(err)
+	if _, writeErr := relay.WriteTo(in, nil); writeErr != nil {
+		t.Fatalf("relay.WriteTo: %v", writeErr)
 	}
 	packets := [][]byte{make([]byte, 64)}
 	sizes := make([]int, 1)