Function tracing::dispatcher::set_default

#[must_use = "Dropping the guard unregisters the dispatcher."]pub fn set_default(dispatcher: &Dispatch) -> DefaultGuard

This is supported on feature="std" only.

Sets the dispatch as the default dispatch for the duration of the lifetime of the returned DefaultGuard

Note: This function required the Rust standard library.
no_std users should use 
set_global_default instead.