const jwt = require('jsonwebtoken')
//...
const makeContext = (req) => {
    if (!req.event || !req.event.headers || !req.event.headers.Authorization) {
        return {} // no auth yet
    }
    const token = req.event.headers.Authorization;
    const decoded = jwt.verify(
        token.replace('Bearer ', ''),
        'secret'
    );
    return {jwt: {...decoded}}
    // Now the token roles will be avaliable in context.jwt.roles
}

const server = new GraphQLServer({
  typeDefs,
  resolvers,
  context: req => ({ ...makeContext(req)
  })
})