如何使结构域成为列表中的值？

I have a list of access rights:

const (
    Everyone = 0
    Owner = 1
    Administrator = 2
)

And a struct representing Routes:

type Route struct {
    Name        string
    Method      string
    Pattern     string
    HandlerFunc http.HandlerFunc
    AccessLevel uint64
}

How can I restrict AccessLevel field value of the Route struct be only one of those const from above?

You can't. Go doesn't support enums. However, you can get close to it. Just introduce a separate type for your access level:

type AccessLevel uint64

and make the consts be of the type:

const (
    Everyone      AccessLevel = 0
    Owner                     = 1
    Administrator             = 2
)

Then define the Field to be of that type:

type Route struct {
    // ...
    AccessLevel AccessLevel
}

Now you can assign those consts, but not a "normal" uint64.

The caveat is that you can still type convert a uint64 to a AccessLevel via AccessLevel(1234).

The only way to impose this type of restriction is by not exporting the field, and doing your checks in any setter method(s).

type Route struct {
    Name        string
    Method      string
    Pattern     string
    HandlerFunc http.HandlerFunc
    accessLevel uint64
}

// AccessLevel getter method
func (r Route) AccessLevel() uint64 {
  return r.accessLevel
}

// SetAccessLevel setter method
func (r Route) SetAccessLevel(value uint64) error {
    if value < 0 || value > 2 {
        return errors.New("AccessLevel must be between 0 and 2, inclusive")
    }
    r.accessLevel = value
    return nil
}