Function layer 

pub fn layer<S>() -> SentryLayer<S>
where
    S: Subscriber + for<'a> LookupSpan<'a>,

👎Deprecated:

Prefer SpanLayer::new() and LogLayer::new(); see SentryLayer docs for migration

Creates a legacy combined Sentry layer.

For most applications, use SpanLayer and LogLayer with explicit filters instead. See SentryLayer for a migration example that preserves the legacy default level selection using all four individual layers, and for differences when migrating custom configuration.