"Web Development with Go" all the records in the query collection Mangodb

Corresponds to select * from table;

package main

import (
	"fmt"
	"log"
	"time"

	"gopkg.in/mgo.v2"
	"gopkg.in/mgo.v2/bson"
)

type Task struct {
	Description string
	Due         time.Time
}

type Category struct {
	Id          bson.ObjectId `bson:"_id,omitempty"`
	Name        string
	Description string
	Tasks       []Task
}

func main() {
	mongoDialInfo := &mgo.DialInfo{
		Addrs:    []string{"localhost"},
		Timeout:  5 * time.Second,
		Database: "taskdb",
		Username: "root",
		Password: "123456",
	}
	session, err := mgo.DialWithInfo(mongoDialInfo)

	if err != nil {
		panic(err)
	}

	defer session.Close()

	session.SetMode(mgo.Monotonic, true)
	c := session.DB("taskdb").C("categories")

	iter := c.Find(nil).Iter()
	result := Category{}
	for iter.Next(&result) {
		fmt.Printf("Category: %s, Description: %s\n", result.Name, result.Description)
		tasks := result.Tasks
		for _, v := range tasks {
			fmt.Printf("Task: %s Due: %v\n", v.Description, v.Due)
		}
	}
	if err = iter.Close(); err != nil {
		log.Fatal(err)
	}

}