Macro dipstick::mod_gauge

macro_rules! mod_gauge {
    ($type_param: ty, $mod_metrics: expr, { $($metric_id: ident: $metric_name: expr),* $(,)* } ) => { ... };
    ($type_param: ty, $mod_metrics: expr, $metric_id: ident: $metric_name: expr) => { ... };
}

Define module-scoped gauges.