mocktracer/mockspan.go
func (s *MockSpan) LogEventWithPayload(event string, payload interface{}) {
	s.LogFields(log.String("event", event), log.Object("payload", payload))
}
func (s *MockSpan) LogEventWithPayload(event string, payload interface{}) {
	s.LogFields(log.String("event", event), log.Object("payload", payload))
}
func ( s * MockSpan ) LogEventWithPayload ( event string , payload interface { } ) { s . LogFields ( log . String ( " " , event ) , log . Object ( " " , payload ) ) }
// LogEventWithPayload belongs to the Span interface
LogEventWithPayload belongs to the Span interface