Configure swagger with Nestjs + Azure functions

I am trying to develop my nestjs using azure functions following this article: https://trilon.io/blog/deploy-nestjs-azure-functions

I have configured Swagger in my application as follows:

...
const options = new DocumentBuilder()
    .setTitle('App title')
    .setDescription('App description')
    .setVersion('1.0')
    .addBearerAuth(
      {
        type: 'http',
        scheme: 'bearer',
        bearerFormat: 'JWT',
      },
      'authorization',
    )
    .addTag('freight')
    .build();

  const document = SwaggerModule.createDocument(app, options);
  SwaggerModule.setup('swagger', app, document);
...

When I run the app in development, I can access my swagger UI by navigating to /swagger, however when I run npm run build && func host start, I receive 500 error, which also happens when I hit a non-existing route.

All other routes that are registered in the application work as expected.

Nestjs has a module you need to load for this. nestjs-openapi

Next you will need to specify a few configuration items.

Note: Main.ts is not used at all.

Sync ports with:

func host start --port 3000

!! Use the app instance within the main.azure.ts. Example assumes global prefix defined above the code below.

...
//config
const config = new DocumentBuilder()
.setTitle('My Title')
.setDescription('My Description')
.setVersion('1.0')
.setBasePath('api-docs')
.build();

const document = SwaggerModule.createDocument(app, config);

SwaggerModule.setup('api-docs', app, document, {
  useGlobalPrefix: true,
});

// order matters here. 
app.init() 
// port that is used for swagger ui. Sync with Az Fx. 
app.listen(3000)

Now you can route to localhost:3000/{global_prefix}/api-docs to load swagger ui.