metric exception

metric/metric.go

@@ -155,6 +155,7 @@ func newMetricImpl(mt MetricType, name string, help string, constLabels map[stri
 	})
 
 	writer = &metric_int64{
+		valptr:     new(int64),
 		key:        key,
 		writerChan: mc.writerChan,
 	}