Open tracing span propagation

[mario-imperato]

What is the proper way to propagate a span over the http request?
Thank you

[mario-imperato]

Need to Inject into the Request.Header the span or by other means? Something along the lines below?
Thank you again.

`httpReq := client.R()

// Transmit the span's TraceContext as HTTP headers on our
// outbound request.
opentracing.GlobalTracer().Inject(span.Context(), opentracing.HTTPHeaders,
opentracing.HTTPHeadersCarrier(httpReq.Header))
`

[FarmerChillax]

refer to #648