GraphQL Invalid IAP credentials: empty token
Tech stacks:
- Google app engine with Identity-Aware Proxy turned on
 - GraphQL with Apollo Server Express
 
Problem
- Cannot enable playground in production
 - Appolo Docs
 
const { ApolloServer } = require('apollo-server');
const { typeDefs, resolvers } = require('./schema');
const server = new ApolloServer({
  typeDefs,
  resolvers,
  introspection: true,
  playground: true,
});
server.listen().then(({ url }) => {
  console.log(`🚀 Server ready at ${url}`);
});
Cause
- Request POST 
/graphqlreturn 401 errors
Digging in that request we got"credentials": "omit" 
Solution
...
const server = new ApolloServer({
  typeDefs,
  resolvers,
  introspection: true,
  playground: {
    settings: {
      'request.credentials': 'include'
    }
  },
});
...