In Koa, can I access Koa-router context at middleware invocation?

Question

I want to pass a parameter into middleware

router.get(
  '/:id',
  myMiddlware({projectid : ctx.request.query.projectid } ),
  async (ctx) => {...}
)

I need to get the value of 'projectid' in the middleware declaration but of course, ctx from Koa-router isn't created yet (I think).

My middleware is defined as :

module.exports.myMiddleware = (fromSource) => async (ctx, next) => {...

I know I'm making a logical mistake somewhere!