feat: cache + paths (#1)

- Added helper function `ExpandUser`
- Added basic cache impmentations for in-memory and file based caches.

Reviewed-on: #1
Co-authored-by: Felipe M. <me@fmartingr.com>
Co-committed-by: Felipe M. <me@fmartingr.com>

cache/memory.go

@@ -0,0 +1,68 @@
+package cache
+
+import (
+	"sync"
+	"time"
+
+	"git.nakama.town/fmartingr/gotoolkit/model"
+)
+
+var _ model.Cache = (*MemoryCache)(nil)
+
+type MemoryCache struct {
+	data   map[string]model.CacheItem
+	dataMu sync.RWMutex
+}
+
+func (c *MemoryCache) Get(key string) (result any, err error) {
+	c.dataMu.RLock()
+
+	item, exists := c.data[key]
+	if !exists {
+		c.dataMu.RUnlock()
+		return result, model.ErrCacheKeyDontExist
+	}
+
+	// Check expiration while still holding the lock
+	if item.TTL != nil && item.TTL.Before(time.Now()) {
+		c.dataMu.RUnlock()
+		_ = c.Delete(key)
+		return result, model.ErrCacheKeyDontExist
+	}
+
+	value := item.Value
+	c.dataMu.RUnlock()
+
+	return value, nil
+}
+
+func (c *MemoryCache) Set(key string, value any, opts ...model.CacheOption) error {
+	item := model.CacheItem{
+		Key:   key,
+		Value: value,
+	}
+
+	for _, opt := range opts {
+		opt(&item)
+	}
+
+	c.dataMu.Lock()
+	c.data[key] = item
+	c.dataMu.Unlock()
+
+	return nil
+}
+
+func (c *MemoryCache) Delete(key string) error {
+	c.dataMu.Lock()
+	delete(c.data, key)
+	c.dataMu.Unlock()
+	return nil
+}
+
+func NewMemoryCache() *MemoryCache {
+	return &MemoryCache{
+		data:   make(map[string]model.CacheItem),
+		dataMu: sync.RWMutex{},
+	}
+}