--- /dev/null
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package keys
+
+var (
+ // Msg is a key used to add message strings to label lists.
+ Msg = NewString("message", "a readable message")
+ // Label is a key used to indicate an event adds labels to the context.
+ Label = NewTag("label", "a label context marker")
+ // Start is used for things like traces that have a name.
+ Start = NewString("start", "span start")
+ // Metric is a key used to indicate an event records metrics.
+ End = NewTag("end", "a span end marker")
+ // Metric is a key used to indicate an event records metrics.
+ Detach = NewTag("detach", "a span detach marker")
+ // Err is a key used to add error values to label lists.
+ Err = NewError("error", "an error that occurred")
+ // Metric is a key used to indicate an event records metrics.
+ Metric = NewTag("metric", "a metric event marker")
+)