fix long run time when the system time was manually set to go back

snowflake.go

@@ -85,7 +85,17 @@ func (sf *SnowFlake) NextId() uint64 {
 			// new timeCycle'time must greater than old
 			if now < curTime {
 				println(fmt.Sprintf("now(%v) < curTime(%v))", now, curTime))
-				continue
+				// 有可能手动设置了系统时间,导致时间后退了
+				// It is possible that the system time was manually set, causing the time to go back
+				if curTime-now <= int64(time.Second/time.Millisecond) {
+					// 如果时间回退在1秒钟之内,则等待时间追上
+					// If the time goes back less than 1 second, sleep for awhile
+					time.Sleep(time.Duration(curTime-now))
+					continue
+				}
+				// 时间回退超过1秒钟,则继续运行,防止"死循环",但是后面生成的id不排除有重复值
+				// If the time goes back more than 1 second, continue running to prevent a "dead loop",
+				// but the id generated later may not unique
 			}
 			newTimeCycle := &timeCycle{
 				sequence: 0,