initialize metrics with negative value prior to collector start

container.go

@@ -19,8 +19,9 @@ type Container struct {
 
 func NewContainer(id, name string) *Container {
 	c := &Container{
-		id:   id,
+		id:      id,
-		name: name,
+		name:    name,
+		metrics: metrics.NewMetrics(),
 	}
 	c.widgets = compact.NewCompact(c.ShortID(), c.ShortName(), c.state)
 	return c

metrics/main.go

@@ -17,6 +17,15 @@ type Metrics struct {
 	MemUsage   int64
 }
 
+func NewMetrics() Metrics {
+	return Metrics{
+		CPUUtil:  -1,
+		NetTx:    -1,
+		NetRx:    -1,
+		MemUsage: -1,
+	}
+}
+
 type Collector interface {
 	Stream() chan Metrics
 	Running() bool