Macro soprintln 

macro_rules! soprintln {
    ($($arg:tt)*) => { ... };
}

soprintln! prints a message prefixed by a truncated timestamp, shared object ID and thread ID.

It is costly, which is why it’s behind a cargo feature AND an environment variable.

To see soprintln output, enable the soprintln cargo feature, and set the SOPRINTLN environment variable to 1.