Go: client is disconnected - mongodb

Question

It's been few weeks since I joined in Gophers team. So far so good.
I started a new project using a fiber web framework to build backend APIs.
I am using MongoDB as my database.
database/db.go
package database
import (
"context"
"log"
"time"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
"go.mongodb.org/mongo-driver/mongo/readpref"
)
var DB *mongo.Database
// InitMongo : Initialize mongodb...
func connectToMongo() {
log.Printf("Initializing database")
client, err := mongo.NewClient(options.Client().ApplyURI("mongodb://localhost:27017"))
if err != nil {
log.Fatal("Could not able to connect to the database, Reason:", err)
}
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
err = client.Connect(ctx)
if err != nil {
log.Fatal("Context error, mongoDB:", err)
}
//Cancel context to avoid memory leak
defer cancel()
defer client.Disconnect(ctx)
// Ping our db connection
err = client.Ping(context.Background(), readpref.Primary())
if err != nil {
log.Fatal("Ping, mongoDB:", err)
}
log.Printf("Database connected!")
// Create a database
DB = client.Database("golang-test")
return
}
// In Golang, init() functions always initialize whenever the package is called.
// So, whenever DB variable called, the init() function initialized
func init() {
connectToMongo()
}
controllers/mongo.controller/mongo.controller.go
package mongocontroller
import (
"log"
"github.com/gofiber/fiber/v2"
service "gitlab.com/.../services/mongoservice"
)
// GetPersons godoc
// #Summary Get persons.
// #Description Get persons
// #Tags persons
// #Produce json
// #Success 200 {object} []service.Person
// #Failure 400 {object} httputil.HTTPError
// #Failure 404 {object} httputil.HTTPError
// #Failure 500 {object} httputil.HTTPError
// #Router /v1/persons [get]
func GetPersons(c *fiber.Ctx) error {
res, err := service.GetPersons()
if err != nil {
log.Fatal("ERROR: in controller...", err)
}
return c.JSON(res)
}
services/mongoservice/mongo.service.go
package mongoservice
import (
"context"
"log"
database "gitlab.com/.../database"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/bson/primitive"
)
// Person : ...
type Person struct {
ID primitive.ObjectID `bson:"_id,omitempty" json:"_id,omitempty"`
Name string `bson:"name,omitempty" json:"name,omitempty"`
Age int `bson:"age,omitempty" json:"age,omitempty"`
}
func GetPersons() ([]Person, error) {
ctx := context.Background()
persons := []Person{}
log.Printf("mongo data...", ctx)
cur, err := database.DB.Collection("persons").Find(ctx, bson.M{})
if err != nil {
log.Fatal(err)
}
// Iterate through the returned cursor.
for cur.Next(ctx) {
var person Person
cur.Decode(&person)
persons = append(persons, person)
}
defer cur.Close(ctx)
return persons, err
}
Here is my data stored in the database:
The problem is, the line cur, err := database.DB.Collection("persons").Find(ctx, bson.M{}) from service always throwing Client is disconnected.
Any help is appreciated!
Thank you.

Answer 1

You are calling defer client.Disconnect(ctx) in the same function which is creating the connection (connectToMongo ) so it will close the connection after calling the function. You should return the connection and close after finishing your task. I mean these parts:
defer cancel()
defer client.Disconnect(ctx)