@lpgeneau reports that module-based build fails with

    2021-07-07 16:37:34 slapos[2415] INFO GOMODSRC /srv/slapgrid/slappart11/srv/runner/software/a12cdf3481c4202ae72cb255d8a6c183/go.work/src/lab.nexedi.com/kirr/git-backup:./...
    2021-07-07 16:37:34 slapos[2415] INFO ../../../../pkg/mod/lab.nexedi.com/kirr/go123@v0.0.0-20210302025843-863c4602a230/xerr/xerr.go:77:2: missing go.sum entry for module providing package github.com/pkg/errors (imported by lab.nexedi.com/kirr/go123/xerr); to add:
    2021-07-07 16:37:34 slapos[2415] INFO   go get lab.nexedi.com/kirr/go123/xerr@v0.0.0-20210302025843-863c4602a230
    2021-07-07 16:37:34 slapos[2415] INFO gowork.goinstall: Non zero exit code (1) while running command.

-> Fix it by updating go123 dependency and running recommended command to update go.sum.

Amends 3c804105 (*: Add Go modules support; Upgrade to latest git2go release)