Can I get some point's about security of my program

Hello, I recently created a simple program similar to called upfast.

Recently I have got interested in how secure it is, and would also get some ideas on how to implement file deletion with a password or anything of that sort.

But what I’m mostly interested in are there any really obvious security mistakes or are there just more way’s to secure it even more.

Note that this is my first ever program written in go and most time was spent looking up syntax.