Function tracing::subscriber::set_default

pub fn set_default<S>(subscriber: S) -> DefaultGuard where
    S: Subscriber + Send + Sync + 'static, 

This is supported on crate feature std only.

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

The default subscriber is used when creating a new Span or Event, if no span is currently executing. If a span is currently executing, new spans or events are dispatched to the subscriber that tagged that span, instead.