examples: add go.mod to make examples a separate module

[chalin]

Fixes #3539
Supersedes #3540

[dfawley]

Looks like the examples test doesn't like this:

https://travis-ci.org/github/grpc/grpc-go/jobs/676263348

Please also run go mod tidy so this creates a go.sum file.

[chalin]

We can't do much (including running go mod tidy) without either:

• A replace rule like:
  go mod edit -replace google.golang.org/grpc@v1.29.0-dev.1=../../
• Or an actual release v1.29.0-dev.1 containing this PR.

I can add the replace rule for the purpose of testing, but of course we won't want to actually commit it.

Any other suggestions?

[dfawley]

Or an actual release v1.29.0-dev.1 containing this PR.

Can we tag this commit with v1.30.0-dev.1 (since this is master and it's on 1.30 now), and reference it in either the same commit -- if that works, which I think it would, even though it's a little paradoxical -- or a subsequent commit?

[chalin]

FYI, with the replace rule in the examples/go.mod file, all tests are passing, see https://travis-ci.org/github/grpc/grpc-go/builds/676339760:

[chalin]

(I'm going to remove the replace rule now)

[chalin]

Without the replace rule, all tests pass except TESTEXTRAS, since v1.30.0-dev.1 is unknown revision: https://travis-ci.org/github/grpc/grpc-go/builds/676345662:

[chalin]

How would you like to proceed? Given that all tests pass when a grpc package can be found (as shown earlier), maybe consider merging this, and tagging the resulting master branch head as v1.30.0-dev.1?

[dfawley]

How would you like to proceed? Given that all tests pass when a grpc package can be found (as shown earlier), maybe consider merging this, and tagging the resulting master branch head as v1.30.0-dev.1?

Did you try tagging your commit in your branch? I'm not sure that will work, but it might be worth a shot. Otherwise I can force merge this and then add the tag after.

[chalin]

Did you try tagging your commit in your branch? I'm not sure that will work, but it might be worth a shot. Otherwise I can force merge this and then add the tag after.

Ok, I've tagged the commit and pushed:

$ git push origin v1.30.0-dev.1
Total 0 (delta 0), reused 0 (delta 0)
To https://github.com/chalin/grpc-go.git
 * [new tag]           v1.30.0-dev.1 -> v1.30.0-dev.1

Can you restart Travis build #9802? (I don't have the permissions to do so.)

[dfawley]

I kicked travis; the EXTRAS run is still failing:

 testing: helloworld 
+go build -o /dev/null ./helloworld/greeter_server/main.go
go: google.golang.org/grpc@v1.30.0-dev.1: reading google.golang.org/grpc/go.mod at revision v1.30.0-dev.1: unknown revision v1.30.0-dev.1

I think this is because go is looking for the tag on github, and it isn't there yet, since it's in this PR. Since it passes with the replace and fails with this message without the replace, then I think we can safely merge this as-is. If github doesn't accept your tag, I'll apply it manually on this commit afterwards.

I'll do this on Monday unless anyone raises any concerns.

[chalin]

Thanks for restarting the build. I also suspected that go wouldn't look for tags on anything other than the main repo's master branch. Monday's is good. Have a great weekend!

[chalin]

I'll do this on Monday unless anyone raises any concerns.

Still slated to try this today?

[chalin]

@dfawley - FYI, now that this has been published, my tests work locally, w/o using the replace rule. Maybe the latest TESTEXTRAS Travis job just needs to be restarted. Could you try that?

[chalin]

Hurray, the build is green! https://travis-ci.org/github/grpc/grpc-go/builds/677804973
Thanks @dfawley for help in moving this forward!

[dfawley]

Everything does seem happy now (it took a few minutes for the go sum DB to be updated, during which time I was mildly concerned)! @chalin will you be making updates to the quick start guide next?

[chalin]

... will you be making updates to the quick start guide next?

Yes, that is at the top of my to-do list!