contrib/gorm.io/gorm.v1: Add err check

[vmlellis]

Add WithErrorCheck option.

An implementation of #915

[songtianyi]

When will this PR be merged, it's very usefull

[felixge]

👋 @vmlellis sorry for the delay on this. I work on the profiler, but I just took a quick look to see if I can help getting this unstuck. PTAL at my comments, addressing them should help with getting this merged.

[felixge]

Is there a reason for using SetTag() instead of tracer.WithError() here? If not, the latter would probably be preferable as it reduces the burden on the reviewer to verify that the two are interchangable.

[freehere107]

@felixge Maybe there ref

dd-trace-go/contrib/jinzhu/gorm/gorm.go

Line 141 in 63dea35

span.SetTag(ext.Error, scope.DB().Error)

[vmlellis]

I changed to this:

	var dbErr error
	if cfg.errCheck(db.Error) {
		dbErr = db.Error
	}
	span.Finish(tracer.WithError(dbErr))

[knusbaum]

I have a few comments.

[knusbaum]

LGTM

[freehere107]

@felixge Hi, Can you help to take a look at this or? At present, datadog will record db record not found, which is troublesome to use

Comments were addressed.

[knusbaum]

Sorry it took a while to get back to this.
There is one nitpick I have and then I will merge this.

[gbbr]

I'm approving & merging, since I see it was thoroughly reviewed by @knusbaum and @felixge with all comments addressed.