Add Key String() function

go/storage/compact_map.go

@@ -1,5 +1,7 @@
 package storage
 
+import "strconv"
+
 type NeedleValue struct {
 	Key    Key
 	Offset uint32 `comment:"Volume offset"` //since aligned to 8 bytes, range is 4G*8=32G
@@ -12,6 +14,10 @@ const (
 
 type Key uint64
 
+func (k Key) String() string {
+	return strconv.FormatUint(uint64(k), 10)
+}
+
 type CompactSection struct {
 	values   []NeedleValue
 	overflow map[Key]NeedleValue