Update sink code to latest go-metrics interface (goadesign#1338)

Author: raphael

.golint_exclude

@@ -2,3 +2,4 @@
 ^examples/cellar/app
 ^examples/cellar/client
 ^examples/cellar/swagger
+^metrics.go

metrics.go

@@ -45,20 +45,13 @@ func NewNoOpSink() metrics.MetricSink {
 // NoOpSink default NOOP metrics recorder
 type NoOpSink struct{}
 
-// SetGauge method
-func (md *NoOpSink) SetGauge(key []string, val float32) {}
-
-// EmitKey method
-func (md *NoOpSink) EmitKey(key []string, val float32) {}
-
-// IncrCounter method
-func (md *NoOpSink) IncrCounter(key []string, val float32) {}
-
-// AddSample method
-func (md *NoOpSink) AddSample(key []string, val float32) {}
-
-// MeasureSince method
-func (md *NoOpSink) MeasureSince(key []string, start time.Time) {}
+func (*NoOpSink) SetGauge(key []string, val float32)                                      {}
+func (*NoOpSink) SetGaugeWithLabels(key []string, val float32, labels []metrics.Label)    {}
+func (*NoOpSink) EmitKey(key []string, val float32)                                       {}
+func (*NoOpSink) IncrCounter(key []string, val float32)                                   {}
+func (*NoOpSink) IncrCounterWithLabels(key []string, val float32, labels []metrics.Label) {}
+func (*NoOpSink) AddSample(key []string, val float32)                                     {}
+func (*NoOpSink) AddSampleWithLabels(key []string, val float32, labels []metrics.Label)   {}
 
 // NewMetrics initializes goa's metrics instance with the supplied
 // configuration and metrics sink

metrics_test.go

@@ -11,22 +11,13 @@ import (
 	"github.com/armon/go-metrics"
 )
 
-// mock metrics
-type mockSink struct{}
-
-func (m *mockSink) SetGauge(key []string, val float32)         {}
-func (m *mockSink) EmitKey(key []string, val float32)          {}
-func (m *mockSink) IncrCounter(key []string, val float32)      {}
-func (m *mockSink) AddSample(key []string, val float32)        {}
-func (m *mockSink) MeasureSince(key []string, start time.Time) {}
-
 var _ = Describe("Metrics", func() {
 	var keys = [6]string{}
 	var metriks *metrics.Metrics
-	var sink *mockSink
+	var sink *goa.NoOpSink
 
 	BeforeEach(func() {
-		sink = &mockSink{}
+		sink = &goa.NoOpSink{}
 
 		var err error
 		metriks, err = metrics.New(metrics.DefaultConfig("UnitTest Service"), sink)