Check authorization header using schema directives

schema.graphql

directive @isAuth on FIELD_DEFINITION

type Mutation {
  addPost(title: String!, content: String! ): Post @isAuth
}

server.js

const { ApolloServer, SchemaDirectiveVisitor } = require("apollo-server-express");
const { defaultFieldResolver } = require("graphql");

class IsAuthDirective extends SchemaDirectiveVisitor {
  visitFieldDefinition(field) {
    const { resolve = defaultFieldResolver } = field;
    field.resolve = async function(...args) {
      const { authUser } = args[2]; // context
      if (!authUser) {
        throw new Error("Invalid token");
      }
      return await resolve.apply(this, args);
    };
  }
}


function context({req}) {
  const token = req.headers.authorization || "";

  // Insert token validation
                  
  return {authUser}
}

const server = new ApolloServer({
  // other options
  context,
  schemaDirectives : {
    isAuth: IsAuthDirective
  };
});