Refactor(proxy): replace with safeConnClose

proxy/shadowsocks.go

@@ -50,11 +50,7 @@ func (ss *Shadowsocks) DialContext(ctx context.Context, metadata *M.Metadata) (c
 	}
 	setKeepAlive(c)
 
-	defer func() {
+	defer safeConnClose(c, err)
-		if err != nil && c != nil {
-			c.Close()
-		}
-	}()
 
 	switch ss.obfsMode {
 	case "tls":

proxy/socks5.go

@@ -39,11 +39,7 @@ func (ss *Socks5) DialContext(ctx context.Context, metadata *M.Metadata) (c net.
 	}
 	setKeepAlive(c)
 
-	defer func() {
+	defer safeConnClose(c, err)
-		if err != nil && c != nil {
-			c.Close()
-		}
-	}()
 
 	var user *socks5.User
 	if ss.user != "" {

proxy/util.go

@@ -16,3 +16,10 @@ func setKeepAlive(c net.Conn) {
 		tcp.SetKeepAlivePeriod(tcpKeepAlivePeriod)
 	}
 }
+
+// safeConnClose closes tcp connection safely.
+func safeConnClose(c net.Conn, err error) {
+	if c != nil && err != nil {
+		c.Close()
+	}
+}