text: import React from 'react';
  import Document, { Html, Head, Main, NextScript } from 'next/document';
  import { ServerStyleSheets } from '@material-ui/core/styles';
  import theme from '../src/theme/default.theme';
  
  export default class MyDocument extends Document {
      render() {
          return (
              <Html lang="en">
                  <Head>
                      {/* PWA primary color */}
                      <meta name="theme-color" content={theme.palette.primary.main} />
                      <link
                          rel="stylesheet"
                          href="https://fonts.googleapis.com/css?family=Roboto:300,400,500,700&display=swap"
                      />
                  </Head>
                  <body>
                      <Main />
                      <NextScript />
                  </body>
              </Html>
          );
      }
  }
  
  // `getInitialProps` belongs to `_document` (instead of `_app`),
  // it's compatible with server-side generation (SSG).
  MyDocument.getInitialProps = async (ctx) => {
      // Resolution order
      //
      // On the server:
      // 1. app.getInitialProps
      // 2. page.getInitialProps
      // 3. document.getInitialProps
      // 4. app.render
      // 5. page.render
      // 6. document.render
      //
      // On the server with error:
      // 1. document.getInitialProps
      // 2. app.render
      // 3. page.render
      // 4. document.render
      //
      // On the client
      // 1. app.getInitialProps
      // 2. page.getInitialProps
      // 3. app.render
      // 4. page.render
  
      // Render app and page and get the context of the page with collected side effects.
      const sheets = new ServerStyleSheets();
      const originalRenderPage = ctx.renderPage;
  
      ctx.renderPage = () =>
          originalRenderPage({
              enhanceApp: (App) => (props) => sheets.collect(<App {...props} />),
          });
  
      const initialProps = await Document.getInitialProps(ctx);
  
      return {
          ...initialProps,
          // Styles fragment is rendered after the app and page rendering finish.
          styles: [...React.Children.toArray(initialProps.styles), sheets.getStyleElement()],
      };
  };
  