docs: migrate dataloaders sample to graph-gophers/dataloader

[zenyui]

This PR replaces the dataloader sample with another using graph-gophers/dataloader.

NOTE: I had originally added this as a second example at the bottom of the old docs, but I found it made the dataloader docs too complex/long. FWIW, it seems dataloaden isn't properly maintained anymore, and IMO codegen is not necessary for this task (so best to avoid it). I'm happy to discuss this, though.

resolves #1714

I have:

• Added tests covering the bug / feature (see testing)
• Updated any relevant documentation (see docs)

[coveralls]

Coverage decreased (-0.01%) to 75.104% when pulling b89043e on zenyui:dataloader-sample into a30b68d on 99designs:master.

[frederikhors]

I think it must be clearly specified that this is an alternative to the other. And maybe we can do two pages, one for each.

Even if the other looks abandoned it could be taken over by the team that took over gqlgen.

Thanks for the wonderful job you have done, @zenyui.

[zenyui]

I think it must be clearly specified that this is an alternative to the other. And maybe we can do two pages, one for each.

Even if the other looks abandoned it could be taken over by the team that took over gqlgen.

Thanks for the wonderful job you have done, @zenyui.

Do you think we should propose graph-gophers/dataloader as the preferred solution? Perhaps we could show the old docs as a "legacy" solution?

In my opinion, we should not be promoting the old library. This dataloader problem does not justify codegen, and go generics will eliminate that need completely, making the old library obsolete.

Thoughts?

[StevenACoffman]

At Khan Academy, we are using graph-gophers/dataloader and fairly happy with it so we aren't really interested in maintaining the vektah/dataloaden. If someone else maintains vektah/dataloaden and adds some really great features, then we can always circle back at that point to the documentation and add back vektah/dataloaden as a choice.

I'm fine with merging this PR as is, but I'm also ok if you want to make additional adjustments.

@zenyui While you are updating documentation, we were contemplating commenting out the autobind in the exampl ein https://github.com/99designs/gqlgen/blob/master/docs/content/config.md per #1860 since when the models directory is empty, it causes an error that is confusing people.

If you get a chance to run through that example without autobind and make sure it still works, I would love to merge that change as well before the next release.

[zenyui]

Alright, appreciate the comments @frederikhors and @StevenACoffman .

At this time, I vote we merge the PR as is and revisit in the future if dataloaden adds new maintainers / features.

[frederikhors]

You convinced me. Also I am using https://github.com/graph-gophers/dataloader successfully.

For me it can be merged.

For the autobind I have already created #1872, @StevenACoffman.

[zenyui]

btw @StevenACoffman seems the github actions workflow broke on an integration test. can you try re-running it?