Add support to traverse into sub-directories

Currently, the code isn't going deep into sub-directories. 

Here's the output of the files scanned.
```
FileName: .git
FileName: .idea
FileName: LICENSE
FileName: README.md
FileName: comments.go
FileName: go.mod
FileName: go.sum
FileName: main.go
FileName: stto
FileName: test
FileName: utils.go
```
