Golang beginner not able solve the problem - mongodb

Question

I would like to make a user login from this method. This has to be in three parts. The same as user registration, but I am not understanding how to do this? Could you please write how I can write a user login logic this same way? It is created using gorilla mux.
One method has to be in db_service.go then one method has to be in login_service.go
one method has to be in login.go.
This is db_service.go code:
/* Used to create a singleton object of MongoDB client.
Initialized and exposed through GetMongoClient().*/
var clientInstance *mongo.Client
//Used during creation of singleton client object in GetMongoClient().
var clientInstanceError error
//Used to execute client creation procedure only once.
var mongoOnce sync.Once
//I have used below constants just to hold required database config's.
const (
CONNECTIONSTRING = "http://127.0.0.1:27017"
AUTH_DB = "Cluster0"
USER_COLLECTION = "user"
)
//GetMongoClient - Return mongodb connection to work with
func GetMongoClient() (*mongo.Client, error) {
//Perform connection creation operation only once.
mongoOnce.Do(func() {
// Set client options
clientOptions := options.Client().ApplyURI(CONNECTIONSTRING)
// Connect to MongoDB
client, err := mongo.Connect(context.TODO(), clientOptions)
if err != nil {
clientInstanceError = err
}
// Check the connection
err = client.Ping(context.TODO(), nil)
if err != nil {
clientInstanceError = err
}
log.Println("Connected Mongodb!")
clientInstance = client
})
return clientInstance, clientInstanceError
}
//CreateIssue - Insert a new document in the collection.
func User_Collection(user *model.User) (*mongo.InsertOneResult, error) {
//Create a handle to the respective collection in the database.
collection := clientInstance.Database(AUTH_DB).Collection(USER_COLLECTION)
//Perform InsertOne operation & validate against the error.
return collection.InsertOne(context.TODO(), user)
}
login_service.go contained code for user registration:
func Register_User(user *model.User) (interface{}, error) {
user.CreatedAt = time.Now().UTC()
user.UpdatedAt = time.Now().UTC()
if result, err := util.User_Collection(user); err == nil {
return result.InsertedID, err
} else {
return nil, err
}
}
User registration code:
func Register(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
var user model.User
if err := json.NewDecoder(r.Body).Decode(&user); err == nil {
if _, err := service.Register_User(&user); err == nil {
w.WriteHeader(http.StatusCreated)
json.NewEncoder(w).Encode(user)
} else {
w.WriteHeader(http.StatusInternalServerError)
json.NewEncoder(w).Encode(err)
}
} else {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
}

Answer 1

Something like this for the handler
func Login(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
var user model.User
if err := json.NewDecoder(r.Body).Decode(&user); err == nil {
if _, err := service.Login_User(&user); err == nil {
json.NewEncoder(w).Encode(user)
} else {
w.WriteHeader(http.StatusInternalServerError)
json.NewEncoder(w).Encode(err)
}
} else {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
}
And something like this for the DB (Need to implement the query instead of insert)
func Login_User(user *model.User) (interface{}, error) {
// Implement this query
if result, err := util.Find_User(user); err == nil {
return result, err
} else {
return nil, err
}
}