$ go build -mod=vendor
go: inconsistent vendoring in <redacted>/madonctl:
github.com/McKael/madon/v2@v2.3.1-0.20190729195747-12ec66101bde: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/McKael/madon/v2@v2.3.1-0.20190113122558-9d8259932fb8
github.com/magiconair/properties@v1.8.1: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/magiconair/properties@v1.8.0
github.com/mattn/go-isatty@v0.0.8: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/mattn/go-isatty@v0.0.4
github.com/pelletier/go-toml@v1.4.0: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/pelletier/go-toml@v1.2.0
github.com/spf13/afero@v1.2.2: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/spf13/afero@v1.1.2
github.com/spf13/cobra@v0.0.5: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/spf13/cobra@v0.0.3
github.com/spf13/jwalterweatherman@v1.1.0: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/spf13/jwalterweatherman@v1.0.0
github.com/spf13/viper@v1.4.0: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/spf13/viper@v1.2.1
github.com/stretchr/testify@v1.3.0: is explicitly required in go.mod, but vendor/modules.txt indicates github.com/stretchr/testify@v1.2.2
golang.org/x/net@v0.0.0-20190724013045-ca1201d0de80: is explicitly required in go.mod, but vendor/modules.txt indicates golang.org/x/net@v0.0.0-20180926154720-4dfa2610cdf3
golang.org/x/sys@v0.0.0-20190726091711-fc99dfbffb4e: is explicitly required in go.mod, but vendor/modules.txt indicates golang.org/x/sys@v0.0.0-20180928133829-e4b3c5e90611
run 'go mod vendor' to sync, or use -mod=mod or -mod=readonly to ignore the vendor directory