What is struct embedding in Go? Named and unnamed embedding.

Embedding structures in Go is a mechanism that allows including one structure into another without explicitly specifying a field, providing a form of inheritance and composition.

Named embedding — when the structure's field has a name and type, for example:

type Address struct {
    City, State string
}

type Person struct {
    Addr Address // named embedding
    Name string
}

Access to fields in this case is through the field name: p.Addr.City.

Unnamed (anonymous) embedding — when only the type is specified in the structure, without a field name:

type Address struct {
    City, State string
}

type Person struct {
    Address // unnamed embedding
    Name string
}

In this case, the fields of the embedded structure are "embedded" into the parent structure, and can be accessed directly: p.City.

This allows implementing composition and code reuse, as well as imitating inheritance, since methods of the embedded structure become methods of the parent structure.