auth.js

// Client
import { setContext } from 'apollo-link-context'

export default setContext(async (_, { headers }) => ({
  headers: {
    ...headers,
    authorization: `Bearer ${localStorage.getItem('token')}`,
  },
}))

getUser.js

const { APP_SECRET } = process.env

export function getUser(req) {
  const Authorization = req.headers.authorization || ''

  if (Authorization) {
    const token = Authorization.replace('Bearer ', '')
    try {
      // Get what you need from JWT (role etc) and pass to context
      const { id } = jwt.verify(token, APP_SECRET) as {
        id: string
      }
      return { id }
    } catch {
      throw new AuthError()
    }
  }

  // No user authenticated
  return null
}

resolvers.js

currentUser: (root, args, ctx, info) => {
  if (ctx.role !== 'admin') {
    throw new Error("not admin");
  }

  return {
    data: 'blah'
  }
},

server.js

const server = new ApolloServer({
  schema,
  context: ({ req }) => ({
    user: getUser(req), // Add user to context to use in resolvers
    services,
    db,
  }),
})