example/dice: Add context propagation (#4644)

CHANGELOG.md

@@ -12,6 +12,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Add `go.opentelemetry.io/otel/bridge/opencensus.InstallTraceBridge`, which installs the OpenCensus trace bridge, and replaces `opencensus.NewTracer`. (#4567)
 - Add scope version to trace and metric bridges in `go.opentelemetry.io/otel/bridge/opencensus`. (#4584)
+- Add context propagation in `go.opentelemetry.io/otel/example/dice`. (#4644)
 
 ### Deprecated
 

example/dice/otel.go

@@ -22,6 +22,7 @@ import (
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
 	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
+	"go.opentelemetry.io/otel/propagation"
 	"go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/resource"
 	"go.opentelemetry.io/otel/sdk/trace"
@@ -50,14 +51,18 @@ func setupOTelSDK(ctx context.Context, serviceName, serviceVersion string) (shut
 		err = errors.Join(inErr, shutdown(ctx))
 	}
 
-	// Setup resource.
+	// Set up resource.
 	res, err := newResource(serviceName, serviceVersion)
 	if err != nil {
 		handleErr(err)
 		return
 	}
 
-	// Setup trace provider.
+	// Set up propagator.
+	prop := newPropagator()
+	otel.SetTextMapPropagator(prop)
+
+	// Set up trace provider.
 	tracerProvider, err := newTraceProvider(res)
 	if err != nil {
 		handleErr(err)
@@ -66,7 +71,7 @@ func setupOTelSDK(ctx context.Context, serviceName, serviceVersion string) (shut
 	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
 	otel.SetTracerProvider(tracerProvider)
 
-	// Setup meter provider.
+	// Set up meter provider.
 	meterProvider, err := newMeterProvider(res)
 	if err != nil {
 		handleErr(err)
@@ -86,6 +91,13 @@ func newResource(serviceName, serviceVersion string) (*resource.Resource, error)
 		))
 }
 
+func newPropagator() propagation.TextMapPropagator {
+	return propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+}
+
 func newTraceProvider(res *resource.Resource) (*trace.TracerProvider, error) {
 	traceExporter, err := stdouttrace.New(
 		stdouttrace.WithPrettyPrint())