Documentation

Documentation will be updated soon until the development has done.
This repo will be integrated with user-service-graphql repository.

This is a new product-service-graphql repository that will use another depedency for graphql.
This repository cloned from product-service-graphql, will do the same thing but some adjustment on dependency.
New GraphQL Depedency used: graph-gophers/graphql-go.
Using @master tag version, because it has support separate resolvers for different operations even it's still not stable release yet.