Implemented GetFreePort utility function to get free port for tests. Updated ACL and PubSub tests to use new GetFreePort functions instead of hardcoded ports

internal/utils.go

@@ -410,3 +410,20 @@ func CompareNestedStringArrays(got [][]string, want [][]string) bool {
 	}
 	return true
 }
+
+func GetFreePort() (int, error) {
+	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
+	if err != nil {
+		return 0, err
+	}
+
+	l, err := net.ListenTCP("tcp", addr)
+	if err != nil {
+		return 0, err
+	}
+	defer func() {
+		_ = l.Close()
+	}()
+
+	return l.Addr().(*net.TCPAddr).Port, nil
+}