From a0e1763cf0b1dd0c445bbfcf9f7f51d639da37e8 Mon Sep 17 00:00:00 2001
From: "larry.nung" <larry.nung@skylinetw.com>
Date: Wed, 6 May 2020 23:24:49 +0800
Subject: [PATCH] fix: InvalidSystemClockException in concurrent

---
 IdGen/IdGenerator.cs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/IdGen/IdGenerator.cs b/IdGen/IdGenerator.cs
index c2b1b6b..3282e0b 100644
--- a/IdGen/IdGenerator.cs
+++ b/IdGen/IdGenerator.cs
@@ -205,12 +205,12 @@ public bool TryCreateId(out long id)
         /// <exception cref="SequenceOverflowException">Thrown when sequence overflows.</exception>
         private long CreateIdImpl(out Exception exception)
         {
-            // Determine "timeslot" and make sure it's >= last timeslot (if any)
-            var ticks = GetTicks();
-            var timestamp = ticks & MASK_TIME;
-
             lock (_genlock)
             {
+                // Determine "timeslot" and make sure it's >= last timeslot (if any)
+                var ticks = GetTicks();
+                var timestamp = ticks & MASK_TIME;
+
                 if (timestamp < _lastgen || ticks < 0)
                 {
                     exception = new InvalidSystemClockException($"Clock moved backwards or wrapped around. Refusing to generate id for {_lastgen - timestamp} ticks");