Is it possible to extend the functionality of a class by adding new properties or fields through interfaces?

In Go, interfaces define a set of methods that a type must implement, but they cannot contain properties or fields. Therefore, it is not possible to extend the functionality of a class (type) by adding new properties through an interface. Interfaces are used to describe behavior, not data structures.

Example of an interface in Go:

type Reader interface {
    Read(p []byte) (n int, err error)
}

If you need to add new fields, this is done through a struct, not an interface.