switch to uint64 cause native word length

internal/cache/cache.go

@@ -16,7 +16,7 @@ const userAgent = "pacman/7.1.0 (Linux x86_64) libalpm/16.0.1"
 
 type Cache struct {
 	cfg       CacheConfig
-	mirrorIdx atomic.Uint32
+	mirrorIdx atomic.Uint64
 	sf        singleflight.Group //prevents duplicate downloads
 	mu        sync.Mutex
 	client    http.Client

internal/cache/helpers.go

@@ -10,7 +10,8 @@ import (
 
 func (c *Cache) nextMirror() string {
 	idx := c.mirrorIdx.Add(1) - 1
-	return c.cfg.mirrorURLs[idx%uint32(len(c.cfg.mirrorURLs))]
+	mirrorCount := uint64(len(c.cfg.mirrorURLs))
+	return c.cfg.mirrorURLs[idx%mirrorCount]
 }
 
 func downloadToDisk(url, destPath string, c http.Client) error {