Goアプリケーションの分散型トレースを実現

func useNewRoundTripper(txn *newrelic.Transaction) (*http.Response, error) {
    client := &http.Client{}
    client.Transport = newrelic.NewRoundTripper(client.Transport)
    request, _ := http.NewRequest("GET", "http://example.com", nil)
    request = newrelic.RequestWithTransactionContext(request, txn)
    return client.Do(request)
}

func external(txn *newrelic.Transaction, req *http.Request) (*http.Response, error) { 
    s := newrelic.StartExternalSegment(txn, req) 
    response, err := http.DefaultClient.Do(req) 
    s.Response = response 
    s.End() 
    return response, err
}

func noGoodForDt(txn *newrelic.Transaction, url string) (*http.Response, error) {
    // Distributed tracing headers are not added to the outgoing request.
    // Use newrelic.NewRoundTripper or newrelicc.StartExternalSegment instead.
    defer newrelic.ExternalSegment{
        StartTime: txn.StartSegmentNow(),
        URL:       url,
    }.End()

    return http.Get(url)
}