revert closer changes

Author: zhangchiqing

storage/operation/reads.go

@@ -130,7 +130,7 @@ func TraverseByPrefix(r storage.Reader, prefix []byte, iterFunc IterationFunc, o
 // When this returned function is executed (and only then), it will write into the `keyExists` whether
 // the key exists.
 // No errors are expected during normal operation.
-func KeyExists(r storage.Reader, key []byte) (exist bool, errExit error) {
+func KeyExists(r storage.Reader, key []byte) (bool, error) {
 	_, closer, err := r.Get(key)
 	if err != nil {
 		// the key does not exist in the database
@@ -140,9 +140,7 @@ func KeyExists(r storage.Reader, key []byte) (exist bool, errExit error) {
 		// exception while checking for the key
 		return false, irrecoverable.NewExceptionf("could not load data: %w", err)
 	}
-	defer func() {
-		errExit = closer.Close()
-	}()
+	defer closer.Close()
 
 	// the key does exist in the database
 	return true, nil
@@ -155,15 +153,13 @@ func KeyExists(r storage.Reader, key []byte) (exist bool, errExit error) {
 //   - storage.ErrNotFound if the key does not exist in the database
 //   - generic error in case of unexpected failure from the database layer, or failure
 //     to decode an existing database value
-func RetrieveByKey(r storage.Reader, key []byte, entity interface{}) (errExit error) {
+func RetrieveByKey(r storage.Reader, key []byte, entity interface{}) error {
 	val, closer, err := r.Get(key)
 	if err != nil {
 		return err
 	}
 
-	defer func() {
-		errExit = closer.Close()
-	}()
+	defer closer.Close()
 
 	err = msgpack.Unmarshal(val, entity)
 	if err != nil {
@@ -176,7 +172,7 @@ func RetrieveByKey(r storage.Reader, key []byte, entity interface{}) (errExit er
 // keys with the format prefix` + `height` (where "+" denotes concatenation of binary strings). The height
 // is encoded as Big-Endian (entries with numerically smaller height have lexicographically smaller key).
 // The function finds the *highest* key with the given prefix and height equal to or below the given height.
-func FindHighestAtOrBelowByPrefix(r storage.Reader, prefix []byte, height uint64, entity interface{}) (errExit error) {
+func FindHighestAtOrBelowByPrefix(r storage.Reader, prefix []byte, height uint64, entity interface{}) error {
 	if len(prefix) == 0 {
 		return fmt.Errorf("prefix must not be empty")
 	}
@@ -186,9 +182,7 @@ func FindHighestAtOrBelowByPrefix(r storage.Reader, prefix []byte, height uint64
 	if err != nil {
 		return fmt.Errorf("can not create iterator: %w", err)
 	}
-	defer func() {
-		errExit = it.Close()
-	}()
+	defer it.Close()
 
 	var highestKey []byte
 
@@ -209,9 +203,7 @@ func FindHighestAtOrBelowByPrefix(r storage.Reader, prefix []byte, height uint64
 		return err
 	}
 
-	defer func() {
-		errExit = closer.Close()
-	}()
+	defer closer.Close()
 
 	err = msgpack.Unmarshal(val, entity)
 	if err != nil {