Dependency update needed

[mdosch]

You are importing github.com/codegangsta/cli which is now forwarding to github.com/urfave/cli. This makes go get -u all fail for me:
go: github.com/codegangsta/cli@v1.22.1: parsing go.mod: unexpected module path "github.com/urfave/cli"

You should replace github.com/codegangsta/cli with github.com/urfave/cli.

[SamWhited]

Also, consider removing your test binaries dependencies from your go.mod file by making cmd/ftest its own module or by renaming cmd/ to _examples/ or .examples which I believe are ignored by go modules.