如何选择匿名字段？

From GoQuery:

type Document struct {
    *Selection
    Url *url.URL
    // contains filtered or unexported fields
}

I want to get *Selection pointer from a *Document variable:

doc, e := goquery.NewDocument("http://www.gemalto.com/companyinfo/careers/")
var sel *goquery.Selection = doc // error!
sel = doc.(*goquery.Selection) // also error!

The unqualified type name acts as the field name

var sel *goquery.Selection = doc.Selection

See the section on Struct Types for details:

A field declared with a type but no explicit field name is an anonymous field, also called an embedded field or an embedding of the type in the struct. An embedded type must be specified as a type name T or as a pointer to a non-interface type name *T, and T itself may not be a pointer type. The unqualified type name acts as the field name.