I think you have problem here with typeDefs: https://github.com/howtographql/graphql-js/blob/ca0d290a7bd29569e67e7438851ebad54db0c697/src/index.js#L27 The schema.graphql file located also in src folder, so why you try to refer it as "./src/schema.graphql" and not simply: "./schema.graphql"?
I think you have problem here with typeDefs:
graphql-js/src/index.js
Line 27 in ca0d290
The schema.graphql file located also in src folder, so why you try to refer it as "./src/schema.graphql" and not simply: "./schema.graphql"?