after.go

siteBucket, err := s3.NewBucket(ctx, "s3-website-bucket", &s3.BucketArgs{
	Website: s3.BucketWebsiteArgs{
		IndexDocument: pulumi.String("index.html"),
	},
})
if err != nil {
	return err
}

before.go

siteBucket, err := s3.NewBucket(ctx, "s3-website-bucket", &s3.BucketArgs{
	Website: map[string]interface{}{
		"indexDocument": "index.html",
	},
})
if err != nil {
	return err
}