server.js

const { ApolloServer, gql } = require('apollo-server')
const { RESTDataSource } = require('apollo-datasource-rest')

class CountriesAPI extends RESTDataSource {
  constructor() {
    super()
    this.baseURL = 'https://restcountries.eu/rest/v2'
  }
  async getAllCountries() {
    return this.get('/all')
  }
}


const typeDefs = gql`
  type Country {
    name: String!
    capital: String!
    population: Int!
  }
  type Query {
    allCountries: [Country!]!
  }
`
	const resolvers = {
	  Query: {
	    allCountries: async (parent, args, { dataSources }) => {
	      return dataSources.countriesAPI.getAllCountries()
	    },
	  },
	}	


const server = new ApolloServer({
  typeDefs,
  resolvers,
  dataSources: () => {
    return {
      countriesAPI: new CountriesAPI(),
    }
  },
})

server.listen().then(({ url }) => console.log(`Server running at ${url}`))