Add simple in-memory cache (#2231)

* Add simple in-memory cache

* Support configuring cache expiration duration

* Support preinitializing cache with items

* Register cache

cache/cache_test.go

@@ -0,0 +1,111 @@
+package cache
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+var (
+	ctx context.Context = context.TODO()
+	key string          = "test"
+	val interface{}     = "hello go-micro"
+)
+
+// TestMemCache tests the in-memory cache implementation.
+func TestCache(t *testing.T) {
+	t.Run("CacheGetMiss", func(t *testing.T) {
+		if _, _, err := NewCache().Context(ctx).Get(key); err == nil {
+			t.Error("expected to get no value from cache")
+		}
+	})
+
+	t.Run("CacheGetHit", func(t *testing.T) {
+		c := NewCache()
+
+		if err := c.Context(ctx).Put(key, val, 0); err != nil {
+			t.Error(err)
+		}
+
+		if a, _, err := c.Context(ctx).Get(key); err != nil {
+			t.Errorf("Expected a value, got err: %s", err)
+		} else if a != val {
+			t.Errorf("Expected '%v', got '%v'", val, a)
+		}
+	})
+
+	t.Run("CacheGetExpired", func(t *testing.T) {
+		c := NewCache()
+		e := 20 * time.Millisecond
+
+		if err := c.Context(ctx).Put(key, val, e); err != nil {
+			t.Error(err)
+		}
+
+		<-time.After(25 * time.Millisecond)
+		if _, _, err := c.Context(ctx).Get(key); err == nil {
+			t.Error("expected to get no value from cache")
+		}
+	})
+
+	t.Run("CacheGetValid", func(t *testing.T) {
+		c := NewCache()
+		e := 25 * time.Millisecond
+
+		if err := c.Context(ctx).Put(key, val, e); err != nil {
+			t.Error(err)
+		}
+
+		<-time.After(20 * time.Millisecond)
+		if _, _, err := c.Context(ctx).Get(key); err != nil {
+			t.Errorf("expected a value, got err: %s", err)
+		}
+	})
+
+	t.Run("CacheDeleteMiss", func(t *testing.T) {
+		if err := NewCache().Context(ctx).Delete(key); err == nil {
+			t.Error("expected to delete no value from cache")
+		}
+	})
+
+	t.Run("CacheDeleteHit", func(t *testing.T) {
+		c := NewCache()
+
+		if err := c.Context(ctx).Put(key, val, 0); err != nil {
+			t.Error(err)
+		}
+
+		if err := c.Context(ctx).Delete(key); err != nil {
+			t.Errorf("Expected to delete an item, got err: %s", err)
+		}
+
+		if _, _, err := c.Context(ctx).Get(key); err == nil {
+			t.Errorf("Expected error")
+		}
+	})
+}
+
+func TestCacheWithOptions(t *testing.T) {
+	t.Run("CacheWithExpiration", func(t *testing.T) {
+		c := NewCache(Expiration(20 * time.Millisecond))
+
+		if err := c.Context(ctx).Put(key, val, 0); err != nil {
+			t.Error(err)
+		}
+
+		<-time.After(25 * time.Millisecond)
+		if _, _, err := c.Context(ctx).Get(key); err == nil {
+			t.Error("expected to get no value from cache")
+		}
+	})
+
+	t.Run("CacheWithItems", func(t *testing.T) {
+		c := NewCache(Items(map[string]Item{key: {val, 0}}))
+
+		if a, _, err := c.Context(ctx).Get(key); err != nil {
+			t.Errorf("Expected a value, got err: %s", err)
+		} else if a != val {
+			t.Errorf("Expected '%v', got '%v'", val, a)
+		}
+	})
+}