cache: use badgerdb (#15)

cache/get.go

@@ -2,17 +2,34 @@ package cache
 
 import (
 	"fmt"
-	"github.com/xujiajun/nutsdb"
+	"github.com/dgraph-io/badger/v3"
 )
 
 func (c *Client) Get(bucket string, key string) ([]byte, error) {
 	var value []byte
-	if err := c.db.View(func(tx *nutsdb.Tx) error {
-		e, err := tx.Get(bucket, []byte(key))
+
+	if err := c.db.View(func(txn *badger.Txn) error {
+		// get key
+		v, err := txn.Get([]byte(fmt.Sprintf("%s_%s", bucket, key)))
 		if err != nil {
-			return fmt.Errorf("%v: %v; get: %w", bucket, key, err)
+			return fmt.Errorf("%v: %v: get error: %w", bucket, key, err)
+
 		}
-		value = e.Value
+
+		// validate value
+		if v.IsDeletedOrExpired() {
+			return fmt.Errorf("%v: %v: get: key does not exist", bucket, key)
+		}
+
+		// read value
+		err = v.Value(func(val []byte) error {
+			value = val
+			return nil
+		})
+		if err != nil {
+			return fmt.Errorf("%v: %v: get: value error: %w", bucket, key, err)
+		}
+
 		return nil
 	}); err != nil {
 		return nil, err