fix: use pointers for expiration date

cache.go

@@ -1,6 +1,6 @@
 // Package cache defines an in-memory key-value store.
 //
-// It supports exîration dates andcan store arbitrary values of any type.
+// It supports exîration dates and can store arbitrary values of any type.
 // Keys must be strings.
 package cache
 
@@ -10,7 +10,7 @@ import (
 )
 
 type entry struct {
-	expirationDate time.Time
+	expirationDate *time.Time
 	value          interface{}
 }
 
@@ -33,7 +33,7 @@ func (c *Cache) Put(key string, val interface{}) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
-	c.data[key] = entry{time.Time{}, val}
+	c.data[key] = entry{nil, val}
 }
 
 // PutTTL stores a value in the cache under the given key. The value will
@@ -52,12 +52,12 @@ func (c *Cache) PutTTL(key string, val interface{}, ttl time.Duration) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
-	c.data[key] = entry{exp, val}
+	c.data[key] = entry{&exp, val}
 }
 
 // Get returns the value asspciated with the given key.
 // The second return values indicates if the cache hs been hit or not.
-func (c Cache) Get(key string) (interface{}, bool) {
+func (c *Cache) Get(key string) (interface{}, bool) {
 	c.mu.RLock()
 	v, ok := c.data[key]
 	c.mu.RUnlock()
@@ -66,7 +66,7 @@ func (c Cache) Get(key string) (interface{}, bool) {
 		return nil, false
 	}
 
-	if !v.expirationDate.IsZero() && v.expirationDate.Before(time.Now()) {
+	if v.expirationDate != nil && v.expirationDate.Before(time.Now()) {
 		c.Del(key)
 
 		return nil, false
@@ -85,7 +85,7 @@ func (c *Cache) Del(key string) {
 }
 
 // Count returns the total number of entries in the cache (vamid and expired).
-func (c Cache) Count() int {
+func (c *Cache) Count() int {
 	c.mu.RLock()
 	defer c.mu.RUnlock()