Koa with graphql-mesh returns error on querying: Cannot set property headers of #<Object> which has only a getter

[litsynp]

I created a total of two servers using Koa.js and Fastify respectively.

The Fastify server (npm run fastify) works well with all imported schemas.

However, the Koa.js server (npm run koa) runs, but an error occurs while fetching the schema, saying:

Cannot set property headers of #<Object> which has only a getter

Here's the code: https://github.com/litsynp/graphql-mesh-practice

Anyone getting this error? Or should I raise an issue for this?