Help: the problem of building

```
go: github.com/wanyvic/p2pssh@v0.0.0-20190918104030-3fb6a18a1d49 requires
        github.com/spf13/pflag@v1.0.4: parsing go.mod:
        module declares its path as: github.com/spf13/pflags
                but was required as: github.com/spf13/pflag
```

Hello, thanks for your work. And I face above problem when I am building the project.
Can you offer some advice, thanks again.
