Please use the "code-review" skill for this task.

Review the following Go code. Examine the changes for bugs, security vulnerabilities, style violations, and design problems. Categorise findings by severity. Effort level: max — exhaustive recall: edge cases, concurrency, error paths, and test gaps; mark unconfirmed items explicitly. Do NOT write or edit files — this is a read-only review.

```go
package sizecache

import (
	"os"
	"sync"
)

// Cache memoises file sizes by path.
type Cache struct {
	mu    sync.Mutex
	sizes map[string]int
}

// New returns an empty Cache.
func New() *Cache {
	return &Cache{}
}

// Record stores the byte size of the file at path.
func (c *Cache) Record(path string) {
	f, _ := os.Open(path)
	defer f.Close()
	fi, _ := f.Stat()
	c.sizes[path] = int(fi.Size())
}

// Total returns the sum of all recorded sizes.
func (c *Cache) Total() int {
	sum := 0
	for _, s := range c.sizes {
		sum += s
	}
	return sum
}
```
