refactor: Simplify getMessages and extractComment

[alexandear]

The PR simplifies implementation of getMessages by replacing bufio.Reader with bufio.Scanner for comment processing. Additionally, leverages strings.TrimPrefix to simplify extractComment.

[ldez]

There is a missing piece: when using a bufio.Scanner, you must check the error (Scanner.Err()).

The previous element was buggy too because the default size of the bufio.NewReader is 4096.

Reader.ReadLine() returns 3 elements: the read section (a line or less), a "prefix" status (to say if the line is fully read), and an error.
When using Reader.ReadLine() you must check the "prefix" to be sure there are no missing elements on the line.

The bufio.Scanner has a size limitation too (64 * 1024).

https://go.dev/play/p/3iSeXkgYTGt

The most "secure" way to read a file is bufio.NewReader but you need to check the "prefix".
In your context, bufio.Scanner can work but the error must be checked.