login endpoint

credentials.go

package root

type Credentials struct {
  Username     string  `json:"username"`
  Password     string  `json:"password"`
}

user.go

type UserService interface {
  ...
  Login(c Credentials) (error, User)
}

user_router.go

func(ur* userRouter) loginHandler(w http.ResponseWriter, r *http.Request) {
  log.Println("loginHandler")
  err, credentials := decodeCredentials(r)
  if err != nil {
    Error(w, http.StatusBadRequest, "Invalid request payload")
    return
  }

  var user root.User
  err, user = ur.userService.Login(credentials)
  if err == nil {
    Json(w, http.StatusOK, user)
  } else {
    Error(w, http.StatusInternalServerError, "Incorrect password")
  }
}

...

func decodeCredentials(r *http.Request) (error,root.Credentials) {
  var c root.Credentials
  if r.Body == nil {
    return errors.New("no request body"), c
  }
  decoder := json.NewDecoder(r.Body)
  err := decoder.Decode(&c)
  return err, c
}

user_service.go

func (p *UserService) Login(c root.Credentials) (error, root.User) {
  model := userModel{}
  err := p.collection.Find(bson.M{"username": c.Username}).One(&model)

  err = model.comparePassword(c.Password)
  if(err != nil) {
    return err, root.User{}
  }

  return err, root.User{
    Id: model.Id.Hex(),
    Username: model.Username,
    Password: "-" }
}