internal/storage/postgres/storage.go
func (s *Storage) Exists(ctx context.Context, accessToken string) (exists bool, err error) {
	span, ctx := opentracing.StartSpanFromContext(ctx, "postgres.storage.exists")
	defer span.Finish()

	start := time.Now()
	labels := prometheus.Labels{"query": "exists"}

	err = s.db.QueryRowContext(ctx, s.queryExists, accessToken).Scan(
		&exists,
	)
	s.incQueries(labels, start)
	if err != nil {
		s.incError(labels)
	}

	return
}
func (s *Storage) Exists(ctx context.Context, accessToken string) (exists bool, err error) {
	span, ctx := opentracing.StartSpanFromContext(ctx, "postgres.storage.exists")
	defer span.Finish()

	start := time.Now()
	labels := prometheus.Labels{"query": "exists"}

	err = s.db.QueryRowContext(ctx, s.queryExists, accessToken).Scan(
		&exists,
	)
	s.incQueries(labels, start)
	if err != nil {
		s.incError(labels)
	}

	return
}
// Exists implements storage interface.