dont fail empty payload

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

yaml.go

@@ -57,6 +57,9 @@ func (c *yamlCodec) ReadBody(conn io.Reader, b interface{}) error {
 	buf, err := ioutil.ReadAll(conn)
 	if err != nil {
 		return err
+	} else if buf == nil {
+		// not needed but similar changes in all codecs
+		return nil
 	}
 
 	return yaml.Unmarshal(buf, b)

yaml_test.go

@@ -0,0 +1,18 @@
+package yaml
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestReadBody(t *testing.T) {
+	s := &struct {
+		Name string
+	}{}
+	c := NewCodec()
+	b := bytes.NewReader(nil)
+	err := c.ReadBody(b, s)
+	if err != nil {
+		t.Fatal(err)
+	}
+}