Macro log_info 

macro_rules! log_info {
    ($target:expr, $msg:expr $(, $key:expr => $val:expr)*) => { ... };
}

Emit a structured log at INFO level via the global logger.

log_info!("server", "listening", "port" => "8080", "host" => "0.0.0.0");
log_info!("server", "started");