✨ It works!

ezcache.go

@@ -1,7 +1,7 @@
 package ezcache
 
 import (
-	"errors"
+	"sync"
 	"time"
 )
 
@@ -10,6 +10,8 @@ type ezc[K comparable, V any] struct {
 	exp      time.Duration
 	cache    map[K]V
 	setTime  map[K]time.Time
+	lock     sync.RWMutex
+	timeLock sync.RWMutex
 }
 
 func New[K comparable, V any](fetcher Fetcher[K, V], exp time.Duration) (Cache[K, V], error) {
@@ -28,11 +30,33 @@ func New[K comparable, V any](fetcher Fetcher[K, V], exp time.Duration) (Cache[K
 	return c, nil
 }
 
-var errUnimpl = errors.New("unimplemented")
-
 func (c *ezc[K, V]) Get(key K) (V, error) {
-	var val V
-	return val, errUnimpl
+	c.timeLock.RLock()
+	setTime, ok := c.setTime[key]
+	c.timeLock.RUnlock()
+	if ok && time.Since(setTime) <= c.exp {
+		c.lock.RLock()
+		val, ok := c.cache[key]
+		c.lock.RUnlock()
+		if ok {
+			return val, nil
+		}
+	}
+
+	val, err := c.fetch(key)
+	if err != nil {
+		return val, err
+	}
+
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.cache[key] = val
+
+	c.timeLock.Lock()
+	defer c.timeLock.Unlock()
+	c.setTime[key] = time.Now()
+
+	return val, nil
 }
 
 func (c *ezc[K, V]) SetFetcher(f Fetcher[K, V]) error {

ezcache_test.go

@@ -42,3 +42,43 @@ func TestNewBadExpiry(tt *testing.T) {
 		})
 	}
 }
+
+func TestGetHappy(t *testing.T) {
+	var hit bool
+	cache, _ := ezcache.New(func(key uint8) (string, error) { hit = true; return fetcher(key) }, 5*time.Second)
+
+	val, err := cache.Get(4)
+	assert.NoError(t, err)
+	assert.Equal(t, "4", val)
+	assert.True(t, hit)
+
+	hit = false
+	val, err = cache.Get(4)
+	assert.NoError(t, err)
+	assert.Equal(t, "4", val)
+	assert.False(t, hit)
+}
+
+func TestGetExpire(t *testing.T) {
+	var hit bool
+	cache, _ := ezcache.New(func(key uint8) (string, error) { hit = true; return fetcher(key) }, 1)
+
+	val, err := cache.Get(4)
+	assert.NoError(t, err)
+	assert.Equal(t, "4", val)
+	assert.True(t, hit)
+
+	hit = false
+	time.Sleep(2)
+	val, err = cache.Get(4)
+	assert.NoError(t, err)
+	assert.Equal(t, "4", val)
+	assert.True(t, hit)
+}
+
+func TestGetError(t *testing.T) {
+	cache, _ := ezcache.New(func(k uint8) (byte, error) { return 0, fmt.Errorf("Nope for %d", k) }, 1)
+
+	_, err := cache.Get(4)
+	assert.ErrorContains(t, err, "Nope for 4")
+}