incorporate graphql-go patch to fix union/interface inline fragments (2nd try)
Created by: sqs
I added a test case and fix for the other error in the 2nd commit https://github.com/graph-gophers/graphql-go/pull/409/commits/653514dff4841b9809b65b90edb1888c1d9334fe of https://github.com/graph-gophers/graphql-go/pull/409. I confirmed that the GraphQL query on the campaigns preview page that previously broke is now working.