feat: add vendor

vendor/github.com/openzipkin/zipkin-go/context.go

@@ -0,0 +1,63 @@
+// Copyright 2022 The OpenZipkin 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 zipkin
+
+import (
+	"context"
+
+	"github.com/openzipkin/zipkin-go/model"
+)
+
+var defaultNoopSpan = &noopSpan{}
+
+// SpanFromContext retrieves a Zipkin Span from Go's context propagation
+// mechanism if found. If not found, returns nil.
+func SpanFromContext(ctx context.Context) Span {
+	if s, ok := ctx.Value(spanKey).(Span); ok {
+		return s
+	}
+	return nil
+}
+
+// SpanOrNoopFromContext retrieves a Zipkin Span from Go's context propagation
+// mechanism if found. If not found, returns a noopSpan.
+// This function typically is used for modules that want to provide existing
+// Zipkin spans with additional data, but can't guarantee that spans are
+// properly propagated. It is preferred to use SpanFromContext() and test for
+// Nil instead of using this function.
+func SpanOrNoopFromContext(ctx context.Context) Span {
+	if s, ok := ctx.Value(spanKey).(Span); ok {
+		return s
+	}
+	return defaultNoopSpan
+}
+
+// NewContext stores a Zipkin Span into Go's context propagation mechanism.
+func NewContext(ctx context.Context, s Span) context.Context {
+	return context.WithValue(ctx, spanKey, s)
+}
+
+// BaggageFromContext takes a context and returns access to BaggageFields if
+// available. Returns nil if there are no BaggageFields found in context.
+func BaggageFromContext(ctx context.Context) model.BaggageFields {
+	if span := SpanFromContext(ctx); span != nil {
+		return span.Context().Baggage
+	}
+	return nil
+}
+
+type ctxKey struct{}
+
+var spanKey = ctxKey{}