# XO1301: malformed xo.mod require, xo.lock, or xo.work line

A `require` line of xo.mod is `require <module path> <version>`: the module path is its git location (its first element is a host name) and the version a tag `vX.Y.Z`. A module is required once. xo.mod has no `replace`, `exclude`, or `retract`; local code is reached through an xo.work workspace. xo.lock lines are `<module path> <version>[/xo.mod] h1:<hash>` and are written by `xo get` and `xo mod tidy`. xo.work lines are `xo <edition>` and `use <dir>`, each dir holding an xo.mod. See core 4.2, 4.3, and decision 0086.

## Example

```xo
// xo.mod
module example.com/api
require github.com/acme/billing 1.4
```

## Fix

```xo
// xo.mod
module example.com/api
require github.com/acme/billing v1.4.0
```

Run `xo explain XO1301` for this text in a terminal, or see
[section 10.6 of the specification](../../spec/core/#106-diagnostic-codes).