Clean and structure logging

Currently, in verbose mode, there's too much logging and most of it is unstructured (doesn't follow a specific format).

There's also no logging library used, and using `fmt.Println` to log everywhere isn't very good for performance or readability.

We want to do the following;
- structured logs as per a particular format
- remove unnecessary log statements
- format data in a readable way
- use a proper logging library with log levels