internal/proto: cleanup code

internal/proto/write_buffer.go

@@ -71,18 +71,16 @@ func (w *WriteBuffer) append(val interface{}) error {
 		} else {
 			w.AppendString("0")
 		}
-	default:
-		if bm, ok := val.(encoding.BinaryMarshaler); ok {
-			bb, err := bm.MarshalBinary()
+	case encoding.BinaryMarshaler:
+		b, err := v.MarshalBinary()
 		if err != nil {
 			return err
 		}
-			w.AppendBytes(bb)
-		} else {
+		w.AppendBytes(b)
+	default:
 		return fmt.Errorf(
 			"redis: can't marshal %T (consider implementing encoding.BinaryMarshaler)", val)
 	}
-	}
 	return nil
 }