Instana tracer implementation

vendor/github.com/instana/go-sensor/context.go

@@ -0,0 +1,42 @@
+package instana
+
+// SpanContext holds the basic Span metadata.
+type SpanContext struct {
+	// A probabilistically unique identifier for a [multi-span] trace.
+	TraceID int64
+
+	// A probabilistically unique identifier for a span.
+	SpanID int64
+
+	// Whether the trace is sampled.
+	Sampled bool
+
+	// The span's associated baggage.
+	Baggage map[string]string // initialized on first use
+}
+
+// ForeachBaggageItem belongs to the opentracing.SpanContext interface
+func (c SpanContext) ForeachBaggageItem(handler func(k, v string) bool) {
+	for k, v := range c.Baggage {
+		if !handler(k, v) {
+			break
+		}
+	}
+}
+
+// WithBaggageItem returns an entirely new SpanContext with the
+// given key:value baggage pair set.
+func (c SpanContext) WithBaggageItem(key, val string) SpanContext {
+	var newBaggage map[string]string
+	if c.Baggage == nil {
+		newBaggage = map[string]string{key: val}
+	} else {
+		newBaggage = make(map[string]string, len(c.Baggage)+1)
+		for k, v := range c.Baggage {
+			newBaggage[k] = v
+		}
+		newBaggage[key] = val
+	}
+	// Use positional parameters so the compiler will help catch new fields.
+	return SpanContext{c.TraceID, c.SpanID, c.Sampled, newBaggage}
+}