Golang结构字段与切片语义：“具有”结构切片与“是”结构切片

I have the following struct representing a Webpage

type Webpage struct {
    url.URL
    references []url.URL
}

I want to represent a website as a collection of Webpages. I am using this struct, but it does not feel like what I am looking for:

type website struct {
    []Webpage
}

I read this as "a website has a slice of Webpages". I want a type that represents "a website is a slice of Webpages".

What type do I use to represent the is relationship instead of the has relationship of a struct field?

type Website []Webpage

Website is slice of Webpage

Of course that's possible. Your structs should be like this.

type Webpage struct {
  url        url.URL
  references []url.URL
}

type Website struct {
  webpages []Webpage
}

So the Website will contain a slice of Webpages. This is common concept while handling with database. If you want to take more example and learn more about the concept you may take a look to this GORM Documentation

Hope it helps.

Edit:
On the book that you follow, there already provided example: https://www.golang-book.com/books/intro/9#section3

type MultiShape struct {
    shapes []Shape
}