我知道了，事实证明我可以使用“ er”约定。

/*
*  Role will ALWAYS reserve the session key "role".
 */
package goserver

const (
    ROLE_KEY string = "role"
)

type Role string

//if index is higher or equal than role, will pass
type RolesHierarchy []Role

type RoleChecker interface {
    IsRole(Role, RolesHierarchy) bool
}

type RoleAssumer interface {
    AssumeRole(ServerSession, Role)
}

type RoleCheckerAssumer interface {
    RoleChecker
    RoleAssumer
}

func (r Role) String() string {
    return string(r)
}

func NewRole(session ServerSession) Role {
    return session.GetValue(ROLE_KEY).(Role)
}

func (this Role) IsRole(role Role, hierarchy RolesHierarchy) bool {
    if role == this {
        return true
    }
    if len(hierarchy) == 0 {
        return false
    }
    var thisI int = 0
    var roleI int = 0
    //Duped roles in hierarchy are verified in verifyConfig during parse
    for i, r := range hierarchy {
        if this == r {
            thisI = i
        }
        if role == r {
            roleI = i
        }
    }
    //TODO I can probably condense what follows into one if
    if thisI == 0 && roleI == 0 {
        return false
    }
    return thisI >= roleI
}

func (this *Role) AssumeRole(session ServerSession, role Role) {
   session.SetValue(ROLE_KEY, role)
   *this = role
}

谢谢Sarathsp，让我正确地考虑了这一点。