init tracer provider and propagator

init-tracer.go

func init() {
	var exporter sdktrace.SpanExporter
	var err error

	// use zipkin exporter
	exporter, err = zipkin.New("http://zipkin:9411/api/v2/spans")
	if err != nil {
		panic(err)
	}

	// use jaeger exporter
	exporter, err = jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint("http://jaeger:14268/api/traces")))
	if err != nil {
		panic(err)
	}

	// new resource with attributes
	resources := resource.NewWithAttributes(
		semconv.SchemaURL,
		semconv.ServiceNameKey.String("webserver-http"),
		semconv.ServiceVersionKey.String("1.0.0"),
	)

	// new tracer provider
	provider := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(exporter),
		sdktrace.WithSampler(sdktrace.AlwaysSample()),
		sdktrace.WithResource(resources),
	)

	// inject tracer provider
	otel.SetTracerProvider(provider)

	// inject propagators
	// use b3 default config (single header)
	otel.SetTextMapPropagator(b3.New())
}