graphql playground bad request on heroku code example

Example: graphql playground bad request on heroku

export const server = new ApolloServer({
  schema: applyMiddleware(makeExecutableSchema({ typeDefs, resolvers })),
  uploads: false,
  introspection: true,
  playground: true,
  formatError: ({ message, positions, originalError }) => ({ message, positions, originalError }),
  formatResponse: ({ data, errors, http }) => ({ data, errors, http })
})