package db

import "context"

type semaphore chan struct{}

func newSemaphore() semaphore {
	return make(semaphore, 1)
}

func (semaphore semaphore) With(ctx context.Context, cb func() error) error {
	select {
	case semaphore <- struct{}{}:
	case <-ctx.Done():
		return ctx.Err()
	}
	defer func() {
		<-semaphore
	}()
	return cb()
}