Function changeNickname

aws-node-graphql-api-with-dynamodb/handler.js:36–45

(firstName, nickname)

  .then(name => `Hello, ${name}.`);

const changeNickname = (firstName, nickname) => promisify(callback =>
  dynamoDb.update({
    TableName: process.env.DYNAMODB_TABLE,
    Key: { firstName },
    UpdateExpression: 'SET nickname = :nickname',
    ExpressionAttributeValues: {
      ':nickname': nickname,
    },
  }, callback))
  .then(() => nickname);

const schema = new GraphQLSchema({
  query: new GraphQLObjectType({