Handle cases here the server time is set to the past, such as dayligh…

…t savings time (#43)

* Calling back the server time can cause an exception in the flow limiting mechanism

If the server time is adjusted back, we need to update the startTime of the bucket and reset the lastTick to 0

* Handle server time going backwards

---------

Co-authored-by: FishJone <[email protected]>

memorystore/store.go

@@ -293,14 +293,22 @@ func (b *bucket) take() (tokens uint64, remaining uint64, reset uint64, ok bool,
 	// Capture the current request time, current tick, and amount of time until
 	// the bucket resets.
 	now := fasttime.Now()
+
+	b.lock.Lock()
+	defer b.lock.Unlock()
+
+	// If the current time is before the start time, it means the server clock was
+	// reset to an earlier time. In that case, rebase to 0.
+	if now < b.startTime {
+		b.startTime = now
+		b.lastTick = 0
+	}
+
 	currTick := tick(b.startTime, now, b.interval)
 
 	tokens = b.maxTokens
 	reset = b.startTime + ((currTick + 1) * uint64(b.interval))
 
-	b.lock.Lock()
-	defer b.lock.Unlock()
-
 	// If we're on a new tick since last assessment, perform
 	// a full reset up to maxTokens.
 	if b.lastTick < currTick {