authLink.js

// Adding Authorization header to Apollo client
const authLink = setContext((event, { headers }) => {
  const token = process.env.BUILD_API_KEY || process.env.GATSBY_CLIENT_API_KEY;

  if (!token) throw new Error('Missing Auth Token');
  const returnValue = {
    headers: {
      ...headers,
      authorization: token ? `Bearer ${token}` : '',
    },
  };

  return returnValue;
});