Macro trace_message 

macro_rules! trace_message {
    ($protocol:expr, $direction:expr) => { ... };
    ($protocol:expr, $direction:expr, $($field:tt)*) => { ... };
}

Create a span for protocol message handling.

Example

use mabi_core::trace_message;

let _span = trace_message!("modbus", "request", unit_id = 1);