Why a custom type in go?

Question

go

The book Effective Go has an example
type ByteSlice []byte
func (slice ByteSlice) Append(data []byte) []byte {
// Body exactly the same as the Append function defined above.
}
Why declare your type "ByteSlice", you can just write func (slice []byte) ....??

Answer 1

A classic example with the area of ​​a figure.
Imagine that you have classes Circle, Square, Rectangle, Triangle. Each calculates the area using their own formula.
Write a method where the list of figures is transferred and it is necessary to calculate their total area?
With the Areaer interface and the "Area() float" type method, this is elementary.
With separate methods, you need a huge switch and know in advance about all possible shapes.
Now imagine that a new requirement has come that the figures have coordinates and it is necessary to calculate the intersecting area? With a type method, this is done quite trivially by chaining calls to the same method on a list of shapes.
In short, to write less code.

Answer 2

it's kind of OOP.
Classes and all.
Everything is in the classroom.
Why do without a class if it is fashionable to make your own class?)

Answer 3

If the type is more complex, such as map[string][]my_package.MyStructure