Reached the recursion limit while auto-dereferencing

Question

I'm working on code to set up multiple database connections, which takes a subdomain and domain as inputs, looks to see if it already has a connection there, and, if not, creates and returns it. If I hardcode the creation of the connections, it works fine, but there will be more databases added in the future, so I'd rather be able to create the connections dynamically, based on inputs.

The working code is just a get():

pub struct AllDbs(pub HashMap<String, sqlx::MySqlPool>);

impl AllDbs {
    pub fn get(&mut self, name: &str) -> Option<sqlx::MySqlPool> {
        self.0.get(name).cloned()
    }
}

// The hardcoded creation of connections
let mut all_dbs: AllDbs = AllDbs(HashMap::new());
let db = sqlx::MySqlPool::connect("mysql://usernmae:[email protected]:3306/default").await.unwrap();
all_dbs.0.insert("test1".to_string(), db);

// The calling code
let db = all_dbs.0.get("test1").unwrap();

The above works fine.

What I'm attempting is a get_or_create()

pub struct AllDbs(pub HashMap<String, sqlx::MySqlPool>);

impl AllDbs {
    pub async fn get_or_create(&mut self, subdomain: &str, domain: &str) -> Option<sqlx::MySqlPool> 
    {
        let key = format!("{}{}", subdomain, domain);
        // If we don't have this database connection already, create it
        if !self.0.contains_key(&key) {
            uri = // create the uri dynamically based on subdomain and domain

            // Store the connection in the hashmap for later use
            let db = sqlx::MySqlPool::connect(&uri).await.unwrap();
            self.0.insert(key.clone(), db);
        }

        return Some(self.0.get(&key).cloned().unwrap());
    }

}

impl Deref for AllDbs {
    type Target = AllDbs;

    fn deref(&self) -> &Self::Target {
        &self
    }
}

// The calling code
let db = all_dbs.get_or_create(&login_data.subdomain, &login_data.domain).await.unwrap();

It's that last line which is producing the error -

reached the recursion limit while auto-dereferencing AllDbs
consider increasing the recursion limit by adding a #![recursion_limit = "256"]

Adding the recursion_limit is not helping, no matter how high I set it, suggesting I've got infinite recursion going on here, meaning I'm missing some basic thing, but I'm not seeing it in the code. FYI I added the Deref implementation because without it, the compiler barfs with a different error:

error[E0596]: cannot borrow data in dereference of rocket::State<AllDbs> as mutable src\routes\login.rs:20:11 | 20 | let db = all_dbs.get_or_create(&login_data.subdomain, &login_data.domain).await.unwrap(); cannot borrow as mutable | help: trait DerefMut is required to modify through a dereference, but it is not implemented for rocket::State<AllDbs>