code: func AnnotateSpanWithGroupInfo(span opentracing.Span, group *tasks.Group, sendConcurrency int) {
  	// tag the span with some info about the group
  	span.SetTag("group.uuid", group.GroupUUID)
  	span.SetTag("group.tasks.length", len(group.Tasks))
  	span.SetTag("group.concurrency", sendConcurrency)
  
  	// encode the task uuids to json, if that fails just dump it in
  	if taskUUIDs, err := json.Marshal(group.GetUUIDs()); err == nil {
  		span.SetTag("group.tasks", string(taskUUIDs))
  	} else {
  		span.SetTag("group.tasks", group.GetUUIDs())
  	}
  
  	// inject the tracing span into the tasks signature headers
  	for _, signature := range group.Tasks {
  		signature.Headers = HeadersWithSpan(signature.Headers, span)
  	}
  }
docs: // AnnotateSpanWithGroupInfo ...