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

Fix

// 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.