Macro template 

macro_rules! template {
    ($template:expr) => { ... };
    ($template:expr, $($key:ident = $value:expr),* $(,)?) => { ... };
}

Template macros for compile-time template rendering

These macros allow embedding template rendering at compile time:

const CONFIG: &str = template!("service = \"{{ name }}\"", name = "my-service");