Macro static_env 

macro_rules! static_env {
    ($(#[$meta:meta])? $vis:vis $var:ident) => { ... };
}

Does the same thing as read_env, but creates static variable for the environment var.

static_env!(MAX_DUCK_SIZE);
// Which will be expanded into
// static MAX_DUCK_SIZE: LazyLock<String> = ...;

fn main() {
  println!("MAX_DUCK_SIZE is {}", *MAX_DUCK_SIZE);
}