Using SSR only without the need to add getServerSideProps on every page

[Charioteer]

Hi Next.js community!

One of my projects requires my team and me to implement a multi-domain frontend which is using an API key for communicating with our backend/API. Since we need an axios instance which is always sending a domain-specific API key for getting ServerSideProps as well as for communicating with our API on the client side, we are using the _app.js' getInitialProps method:

MyApp.getInitialProps = async appContext => {
  console.log(appContext.ctx.req) // 1st log entry: correct request object, 2nd log entry: undefined

  const appProps = await App.getInitialProps(appContext)

  const apiClient = getApiClient()

  const apiKey = appContext.ctx.req['apiKey']
  authedClient.defaults.headers['X-Api-Key'] = apiKey
  apiClient.defaults.headers['X-Api-Key'] = apiKey
  //...
}

appContext.ctx.req['apiKey'] is set by our custom express server implementation.

We've assumed that - as stated here - the usage of getInitialProps in _app.js will cause "every page in your app to be server-side rendered.". In contrast, however, we have to add the following snippet on each and every page to get the API key set correctly. Otherwise appContext.ctx.req is undefined:

export async function getServerSideProps({ req }) {
  return {
    props: {},
  }
}

To be more precise: without the above-mentioned code snippet the correctly rendered page flashes for about 2 seconds and console.log(appContext.ctx.req) prints twice: the first time it prints the correct request object. The second time it prints undefined leading to an error message on our page. We suspect that somehow the initial render is server side but there is some kind of a second render which causes ctx.req to be undefined.

Unfortunately we didn't find a way to "tell" Next.js to server-side-render every single page without exceptions. We basically want to opt-out of SSG completly.

Did we miss something? Shouldn't appContext.ctx.reqbe undefined in this case? Did we misunderstand _app.js' getInitialProps()?

Thank you in advance!