fix: update lego.

vendor/go.opencensus.io/stats/view/export.go

@@ -0,0 +1,58 @@
+// Copyright 2017, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package view
+
+import "sync"
+
+var (
+	exportersMu sync.RWMutex // guards exporters
+	exporters   = make(map[Exporter]struct{})
+)
+
+// Exporter exports the collected records as view data.
+//
+// The ExportView method should return quickly; if an
+// Exporter takes a significant amount of time to
+// process a Data, that work should be done on another goroutine.
+//
+// It is safe to assume that ExportView will not be called concurrently from
+// multiple goroutines.
+//
+// The Data should not be modified.
+type Exporter interface {
+	ExportView(viewData *Data)
+}
+
+// RegisterExporter registers an exporter.
+// Collected data will be reported via all the
+// registered exporters. Once you no longer
+// want data to be exported, invoke UnregisterExporter
+// with the previously registered exporter.
+//
+// Binaries can register exporters, libraries shouldn't register exporters.
+func RegisterExporter(e Exporter) {
+	exportersMu.Lock()
+	defer exportersMu.Unlock()
+
+	exporters[e] = struct{}{}
+}
+
+// UnregisterExporter unregisters an exporter.
+func UnregisterExporter(e Exporter) {
+	exportersMu.Lock()
+	defer exportersMu.Unlock()
+
+	delete(exporters, e)
+}