CloseSpan logs event finishes span.

InitTracing connects the calling service to Zipkin and initializes the tracer.

LogEventToOngoingSpan extracts span from context and adds LogEvent.

SpanFromContext gets zipkin span from http request.

StartChildSpanFromContext starts a child span from span within the supplied context, if available.

StartSpanFromContextWithLogEvent starts span from context with logevent.

WithTracing sets up zipkin tracing for given HTTP handler if r.Trace is true.