Added integration support for DataDog APM Tracing

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/context.go

@@ -0,0 +1,42 @@
+package tracer
+
+import (
+	"context"
+
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
+)
+
+type contextKey struct{}
+
+var activeSpanKey = contextKey{}
+
+// ContextWithSpan returns a copy of the given context which includes the span s.
+func ContextWithSpan(ctx context.Context, s Span) context.Context {
+	return context.WithValue(ctx, activeSpanKey, s)
+}
+
+// SpanFromContext returns the span contained in the given context. A second return
+// value indicates if a span was found in the context. If no span is found, a no-op
+// span is returned.
+func SpanFromContext(ctx context.Context) (Span, bool) {
+	if ctx == nil {
+		return &internal.NoopSpan{}, false
+	}
+	v := ctx.Value(activeSpanKey)
+	if s, ok := v.(ddtrace.Span); ok {
+		return s, true
+	}
+	return &internal.NoopSpan{}, false
+}
+
+// StartSpanFromContext returns a new span with the given operation name and options. If a span
+// is found in the context, it will be used as the parent of the resulting span. If the ChildOf
+// option is passed, the span from context will take precedence over it as the parent span.
+func StartSpanFromContext(ctx context.Context, operationName string, opts ...StartSpanOption) (Span, context.Context) {
+	if s, ok := SpanFromContext(ctx); ok {
+		opts = append(opts, ChildOf(s.Context()))
+	}
+	s := StartSpan(operationName, opts...)
+	return s, ContextWithSpan(ctx, s)
+}