You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mod.rs
    path of file: ./repos/rustodon/src/db
    
    the code of the file until where you have to start completion: // silence warnings due to diesel-rs/diesel#1785
#![allow(proc_macro_derive_resolution_fallback, unused_imports)]

pub use diesel::connection::Connection as DieselConnection;
use diesel::pg::PgConnection;
use
    
    fn from_request(request: &'a Request<'r>) -> request::Outcome<Connection, ()> {
        // retrieve the database connection from Rocket's managed data
        let pool = request.guard::<State<Pool>>()?;

        match pool.get() {
            // .get() a connection from the pool
            Ok(conn) => Outcome::Success(Connection(conn)),
            Err(_) => Outcome::Failure((Status::ServiceUnavailable, ())),
        }
    }