1. Move to $GOPATH/src/my-first-beego-project/controllers and create firstcontroller.go, as follows:

package controllers
import "github.com/astaxie/beego"
type FirstController struct 
{
  beego.Controller
}
type Employee struct 
{
  Id int `json:"id"`
  FirstName string `json:"firstName"`
  LastName string `json:"lastName"`
}
type Employees []Employee
var employees []Employee
func init() 
{
  employees = Employees
  {
    Employee{Id: 1, FirstName: "Foo", LastName: "Bar"},
    Employee{Id: 2, FirstName: "Baz", LastName: "Qux"},
  }
}
func (this *FirstController) GetEmployees() 
{
  this.Ctx.ResponseWriter.WriteHeader(200)
  this.Data["json"] = employees
  this.ServeJSON()
}

2. Move to $GOPATH/src/my-first-beego-project/routers and edit router.go to add GET mapping /employees, which will be handled by the GetEmployees handler defined in FirstController, as follows: 

package routers
import 
(
  "my-first-beego-project/controllers"
  "github.com/astaxie/beego"
)
func init() 
{
  beego.Router("/", &controllers.MainController{})
  beego.Router("/employees", &controllers.FirstController{},
  "get:GetEmployees")
}

3. Run the project using the following command:

$ bee run