fix: 修复forward不释放，一直创建新的forward，耗尽文件句柄

hrp/internal/builtin/utils.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"math"
 	"math/rand"
+	"net"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -484,6 +485,20 @@ func ConvertToStringSlice(val interface{}) ([]string, error) {
 	return nil, fmt.Errorf("invalid type for conversion to []string")
 }
 
+func GetFreePort() (int, error) {
+	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
+	if err != nil {
+		return 0, errors.Wrap(err, "resolve tcp addr failed")
+	}
+
+	l, err := net.ListenTCP("tcp", addr)
+	if err != nil {
+		return 0, errors.Wrap(err, "listen tcp addr failed")
+	}
+	defer func() { _ = l.Close() }()
+	return l.Addr().(*net.TCPAddr).Port, nil
+}
+
 func GetCurrentDay() string {
 	now := time.Now()
 	// 格式化日期为 yyyyMMdd