rust externs

gistfile1.txt

macro_rules! externs {
    ( $( $x:ident ),* ) => {
        $(
            extern crate $x;
        )*
    };
}

externs![rocket, rocket_contrib, serde_json, 
chrono, dotenv, postgres, r2d2, 
r2d2_postgres, r2d2_diesel, tera, 
serde_derive, toml, glob];