code: func AnnotateSpanWithChainInfo(span opentracing.Span, chain *tasks.Chain) {
  	// tag the span with some info about the chain
  	span.SetTag("chain.tasks.length", len(chain.Tasks))
  
  	// inject the tracing span into the tasks signature headers
  	for _, signature := range chain.Tasks {
  		signature.Headers = HeadersWithSpan(signature.Headers, span)
  	}
  }
docs: // AnnotateSpanWithChainInfo ...