Implement both TextMarshaler and TextUnmarshaler for codec

If a type only defines one-half of the symmetry (e.g. it implements MarshalJSON() but not UnmarshalJSON() ), then that type doesn't satisfy the codec encoding/decoding check and instead codec will not encode or decode the item using the special interface methods.

cnf/cnf.go

@@ -23,10 +23,6 @@ var Settings *Options
 
 type Kind int
 
-func (k Kind) MarshalText() (data []byte, err error) {
-	return []byte(k.String()), err
-}
-
 func (k Kind) String() string {
 	switch k {
 	default:
@@ -42,6 +38,14 @@ func (k Kind) String() string {
 	}
 }
 
+func (k Kind) MarshalText() (data []byte, err error) {
+	return []byte(k.String()), err
+}
+
+func (k Kind) UnmarshalText(text []byte) error {
+	return nil
+}
+
 const (
 	// Root access
 	AuthKV Kind = iota