code: func LogRequest(span opentracing.Span, r *http.Request) {
  	if span != nil && r != nil {
  		ext.HTTPMethod.Set(span, r.Method)
  		ext.HTTPUrl.Set(span, r.URL.String())
  		span.SetTag("http.host", r.Host)
  	}
  }
docs: // LogRequest used to create span tags from the request.