接口[golang]中的字段？

is there any solution to force struct have specific property(defined in interface)?
or define a property(attribute,field) in interface?.
as i see interface is always accept method not property?. (https://gobyexample.com/interfaces)

type geo interface {
    PrintType()
    typ string//not function , but field
}
type circle struct {
    typ string
}

func (c circle) PrintType() {
    fmt.Println(c.typ)
}

thanks

Interfaces are about methods only, not properties, because interfaces are about behavior. So there is no way to force a struct to have something. Rather the preferred method is to have an accessor to that member.