CopySpan creates a new context from parentCtx, with only the trace span copied over from spanCtx, if it has any.

FromContext returns the Span from a Context if present.

NewContext returns a context based on parent with a new Span value.

NewSpan creates a new Span with the currently installed tracing plugin.

NewSpanFromContext returns a new Span whose parent is the Span from the given Context if present, or a new Span with no parent if not.

RegisterSpanFactory should be called by a plugin during init() to install a factory that creates Spans for that plugin's tracing framework.

Span represents a unit of work within a trace.

SpanFactory is an interface for creating spans or extracting them from Contexts.