NewRoundTripper for injected http clients about go-agent

[willnewrelic]

Hi @ianlopshire

We agree! Great idea! We plan to add this functionality in the next release.

For backwards compatibility, we plan on keeping the NewRoundTripper prototype the same: Consumers will simply be encouraged to use nil for the Transaction parameter:

client := new(http.Client)
client.Transport = newrelic.NewRoundTripper(nil, c.Transport)

We also plan to update StartExternalSegment with similar behavior: If transaction is nil, we will look in the request's context for a transaction.

[cgilling]

Great to see this, as the previous implementation seemed to make it pretty much impossible to cache connections

[willnewrelic]

This functionality has now been released in 2.2.0!

https://godoc.org/github.com/newrelic/go-agent#NewRoundTripper now takes a nil transaction.