How to preload lazy_static variables in Rust?

Question

I use Rust's lazy_static crate to assign a frequently used database object to a global variable but I do not want lazy loading. Is there a way to trigger lazy_static to preload the variable or is there a better way to achieve this? All the functions of the database are expensive and it seems to not be enough to assign a reference.

lazy_static! {
    static ref DB: DataBase = load_db();
}
 
/// this is too slow
#[allow(unused_must_use)] 
pub fn preload1() { GRAPH.slow_function(); }

/// this does not cause lazy static to trigger
pub fn preload2() { let _ = &GRAPH; }

Answer 1

_ does not bind , so use a variable name (with leading underscore to avoid the lint):

use lazy_static::lazy_static; // 1.4.0

struct DataBase;
fn load_db() -> DataBase {
    println!("db loaded");
    DataBase
}

lazy_static! {
    static ref DB: DataBase = load_db();
}

fn main() {
    let _db: &DataBase = &*DB; // prints "db loaded"
}

playground