是否可以将变量“嵌入式变量”添加到结构中？

type UserModel struct {
    ...
}

func (u *UserModel) C() string {
    return "system_users"
}

The above will assign an embedded struct to the type UserModel, does Go allow the same to be done with vars or consts?

Something like

var (u *UserModel) C = "system_users"

You get the idea.

Methods

Methods is a functions with receivers bound to a types. Receiver could take a value or a pointer to a type which method bound to.

Go by example provides this nice example:

type rect struct {
    width, height int
}

// This `area` method has a _receiver type_ of `*rect`.
func (r *rect) area() int {
    return r.width * r.height
}

// Methods can be defined for either pointer or value
// receiver types. Here's an example of a value receiver.
func (r rect) perim() int {
    return 2*r.width + 2*r.height
}

And yes you can define methods on almost all existing types except interface. Also it must be local type (defined in a package not built-in)

type Int int

func (i Int) Add(j Int) Int {
    return i + j
}

Embedding

Generalizing "Effective Go" a bit:

The methods of embedded types come along for free. Which means that if type B embedded to type A than type A not only has its own methods it also has methods of type B.

Extending previous example:

type parallelogram struct {
    rect // Embedding. parallelogram has area and perim methods
    depth int
}

func (p parallelogram) volume () int { // Extending rect
    // Volume logic
}