Oskicat, UC Berkeley's public catalog, is very helpful in finding United States government information at UCB. The best search strategy is to use Oskicat's Advanced Keyword Search tab. Once at the Advanced Keyword Search screen, change the first drop-down to Author and enter United States in the box next to it:
Leave the remaining drop-downs as Any Field and enter your search terms in those boxes (think of broad search terms for this step). You may also change the second drop-down to Author and add the name of a particular agency or department to find publications from that agency. You also have the option to limit by date at the bottom of the search page, or UCB library location if needed.
Many, but not all, of the online government titles in OskiCat can be accessed by anyone. If you need a tangible title, note its physical location, call number, and status--UC Berkeley has over twenty libraries on campus and you wouldn't want to be in one library when the title you want is in another building. OskiCat can also text you this information.
The Catalog of Government Publications is run by the Government Publishing Office. The catalog will work, but it will not be updated after the shutdown begins. Also, some of the PURL links in the catalog (purl.gpo.gov) may not work during the shutdown.