Function fetch 

pub async fn fetch(
    cache: &SchemaCache,
    url: &str,
) -> Result<Catalog, Box<dyn Error + Send + Sync>>

Fetch a schema registry catalog by URL.

The URL is first resolved via resolve_urls to expand shorthand notations like github:org/repo. For GitHub shorthands without an explicit branch, both main and master are tried.

Errors

Returns an error if none of the resolved URLs can be fetched or parsed.