fix some shutdown bugs and so on

middleware/metrics.go

@@ -43,6 +43,7 @@ func NewMetrics(bufferSize int, flushTimeout time.Duration, file string) *Metric
 		c:      make(chan RequestMetric, bufferSize),
 		ticker: time.NewTicker(flushTimeout),
 		file:   file,
+		stop:   make(chan struct{}),
 	}
 }
 

middleware/rate-limit.go

@@ -31,6 +31,7 @@ func NewLimiter(maxRequests int, refills int, refillInterval time.Duration, clea
 		bucketRefill:   refills,
 		rwLock:         &sync.RWMutex{},
 		rateChannel:    make(chan string),
+		stop:           make(chan struct{}),
 	}
 }