Updates echo package version to v4.

[1995parham]

Echo has released its new version with Go module support. Its import path has been changed to github.com/labstack/echo/v4 and I change it in the apmecho.

[axw]

@1995parham thanks for opening a PR for this!

This breaks backwards compatibility, so it would require a major version bump of the agent. However, I think we should maintain support for both versions for some time, as not everyone is using modules yet.

I'm not sure what the best thing to do is. Perhaps introduce apmecho/v4, which is a copy of apmecho but with the import paths changed?

[1995parham]

I agree with your idea, we can create apmecho/v4 that works with version 4 of echo and save apmecho for backward compatibility. I try to do it in this PR and let you know.

[1995parham]

@axw I tried to provide a separate module for version 4 of Echo.

[axw]

Thanks @1995parham!

Looking good, just a few little things to update.

Besides what I commented on inline, please run "go generate ./scripts" from the top level of the repo, and commit the updated file "scripts/Dockerfile-testing". That will fix the error in https://travis-ci.org/elastic/apm-agent-go/jobs/507736184.

[axw]

The changes to the existing go.mod and go.sum can be reverted now, right?

[1995parham]

Yes, I forgot that.

[axw]

go.mod and go.sum are still modified, can you please remove the changes from the diff altogether? You can do this by resetting those files to their contents in the master branch:

git reset master go.mod go.sum
git checkout go.mod go.sum
git commit -a -m "Revert changes to go.mod/go.sum"

[axw]

Because of how echo adds the version in the module definition, rather than as a directory, this package won't build with Go 1.8 (see https://travis-ci.org/elastic/apm-agent-go/jobs/507736180).

Can you please add a build constraint for 1.9+ to each of the Go files in this new package? Look for "// +build go1.9" in the files in apmgocql for an example, if you're unfamiliar with doing that.

[1995parham]

That is an awesome idea 👍 I added the build tags in v4 files.

[axw]

The package doc needs to be directly before the "package apmecho" line for it to show up in godoc properly. Can you please change it so it looks like this:

// +build go1.9

// Package apmecho...
package apmecho

[axw]

go.mod and go.sum are still modified, can you please remove the changes from the diff altogether? You can do this by resetting those files to their contents in the master branch:

git reset master go.mod go.sum
git checkout go.mod go.sum
git commit -a -m "Revert changes to go.mod/go.sum"

[axw]

Thanks @1995parham! There's something going wrong with CI to do with module verification. I think it's a bug in the verification code, and not your changes. I will try to look into it tomorrow.

[1995parham]

@axw Thanks for your time and your reviews. I am available if any changes will need.

[codecov-io]

Codecov Report

Merging #477 into master will decrease coverage by 0.59%.
The diff coverage is 85.48%.

@@            Coverage Diff            @@
##           master     #477     +/-   ##
=========================================
- Coverage   84.41%   83.81%   -0.6%     
=========================================
  Files         112      113      +1     
  Lines        7095     6795    -300     
=========================================
- Hits         5989     5695    -294     
  Misses        794      794             
+ Partials      312      306      -6

Impacted Files	Coverage Δ
module/apmechov4/middleware.go	85.48% <85.48%> (ø)
gocontext.go	84.09% <0%> (-12.21%)	⬇️
error.go	94.88% <0%> (-2.61%)	⬇️
tracer.go	86.09% <0%> (-1.3%)	⬇️
span.go	86.82% <0%> (-0.95%)	⬇️
transaction.go	94.64% <0%> (-0.36%)	⬇️
modelwriter.go	95.93% <0%> (+0.83%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3c9177c...429791a. Read the comment docs.

[axw]

@1995parham the go tool is getting confused by the "v4" path, thinking it signifies a major version path for the apmecho module.

The best idea I've come up with is to rename it to "go.elastic.co/apm/module/apmechov4", but I'm open to other ideas if you have any.

[1995parham]

@axw Personally I prefer /v4 but because of issues I think creates another top-level module is the only way. I will try it and let you know. Again thanks for your time.

[axw]

LGTM, just a couple of minor changes required.

[axw]

This should now be "Package apmechov4 ..."
(golint is complaining)

[axw]

This (and below) needs to be changed from apmecho/v4 to apmechov4

[axw]

Thanks again for your contribution @1995parham!