in pages/_document.tsx [7:16]
static async getInitialProps(ctx) {
const initialProps = await Document.getInitialProps(ctx);
const page = ctx.renderPage((App) => (props) => (
<StyletronProvider value={styletron}>
<App {...props} />
</StyletronProvider>
));
const stylesheets = styletron.getStylesheets() || [];
return { ...initialProps, page, stylesheets };
}