graphql-go Federation support

[hwillson]

There is an interesting discussion about adding Federation support to graphql-go here: graphql-go/graphql#492

graphql-go is intended to be more of a graphql-js clone, which means Federation support doesn't necessarily belong in the library itself, but it looks like there are API changes that could be made to graphql-go to make it easier to use with Federation. The above linked to issue dives into this a bit (graphql-go/graphql#492 (comment)), but we'll need to validate this and see if any other changes are needed (see also graphql-go/graphql#541). If we can help get these changes in place, we can then think about potentially creating a Go based Federation helper library, like we've done with @apollo/subgraph (JS/Node) and federation-jvm (Java/JVM).

[codebdy]

It is a good idea, I need Federation support

[hwillson]

We're going to prep a PR to add Federation enabling changes in graphql-go.

[dariuszkuc]

POC is available at dariuszkuc/graphql@v0.9.0-federation.

Example implementation of the testing schema used in this repo: https://github.com/dariuszkuc/graphql/tree/federation/examples/federation (ftv1 tracing is not supported, all other tests are 🟢)

graphql-go/graphql PRs:

• fix String/Name methods on the List type graphql-go/graphql#651
• feat: initial suport for applied directives graphql-go/graphql#652
• fix: return valid object description graphql-go/graphql#653

Once above PRs are merged we can create and publish separate federation module.

[hwillson]

While we wait for feedback (and 🤞 our graphql-go PR's to be merged), we're going to go ahead and add graphql-go tests to this repo, pointing to the above fork for now.

[hwillson]

Re-opening this issue to use as our tracking issue for getting @dariuszkuc's awesome graphql-go + Federation work hopefully merged into the project.