Methods

Methods are similar to functions but they operate on instances of a specific type (receiver).
There is no this orself keyword in Go but it is a convention to use the first letter of the receiver.

type rectangle struct {
    width, height float64
}

func (r rectangle) Area() float64 {
    return r.Width * r.Height
}

Value and pointer receivers

A value receiver (t T) uses a copy of the original value.
To modify the original value a pointer receiver (t *T) is needed.
For consistency, all methods on a type should use the same receiver type, even if not needed.