Using MongoDB in Go: A Complete Guide

MongoDB is a high-performance, open source, document-based NoSQL database that is widely used in web applications, big data and cloud computing. The Go language is a programming language that is fast, has high development efficiency, and has strong code maintainability. This article will give you a complete introduction to how to use MongoDB in Go language.

1. Install MongoDB

Before using MongoDB, you need to install MongoDB in your system. Under Linux systems, you can install it through the following command:

sudo apt-get update
sudo apt-get install mongodb
sudo systemctl start mongodb

Under Windows systems, you can go to the MongoDB official website to download the corresponding version of the installation package and follow the prompts to install it.

2. Connecting to MongoDB

In the Go language, using MongoDB requires installing the third-party package mgo. It can be installed through the following command:

go get gopkg.in/mgo.v2

Next, we can write the following code to connect to MongoDB:

package main

import (
    "fmt"
    "gopkg.in/mgo.v2"
)

func main() {
    session, err := mgo.Dial("localhost:27017")
    if err != nil {
        panic(err)
    }
    defer session.Close()

    collection := session.DB("test").C("users")
    fmt.Println(collection)
}

This code will connect to the test database in MongoDB and return the users collection. Among them, session is a variable of mgo.Session type, representing the connection between the client and MongoDB. The defer keyword will ensure that session.Close() is executed before the end of the program, that is, the connection is closed. Finally, we output the collection value through the fmt.Println() function to verify whether the database connection is successful.

3. Insert and query documents

In MongoDB, a document is the basic unit of data, similar to a row in a relational database. Go language can insert and query documents through the mgo package. The following code can insert a document into the users collection in MongoDB:

package main

import (
    "fmt"
    "gopkg.in/mgo.v2"
    "time"
)

type User struct {
    Name     string `bson:"name"`
    Age      int    `bson:"age"`
    Email    string `bson:"email"`
    CreateAt time.Time `bson:"create_at"`
}

func main() {
    session, err := mgo.Dial("localhost:27017")
    if err != nil {
        panic(err)
    }
    defer session.Close()

    collection := session.DB("test").C("users")

    user := User{
        Name:     "Alice",
        Age:      28,
        Email:    "alice@example.com",
        CreateAt: time.Now(),
    }
    err = collection.Insert(user)
    if err != nil {
        panic(err)
    }

    var result []User
    err = collection.Find(nil).Sort("-create_at").Limit(10).All(&result)
    if err != nil {
        panic(err)
    }
    fmt.Println(result)
}

Among them, we first define a User structure to describe the document in the database. In the main function, we first create a variable user of type User and initialize its fields. Then, we insert it into the users collection through the collection.Insert() method. Finally, we used the collection.Find() method to query all documents in the users collection, sorted them in reverse order according to the create_at field, limited the number of returned results to 10, and finally output the query results.

4. Update and delete documents

In MongoDB, you can update documents through the Update method and delete documents through the Remove method. The following code can update the age of the document named Alice to 30 in the users collection and then delete it:

user := User{
    Name:     "Alice",
    Age:      30,
    Email:    "alice@example.com",
    CreateAt: time.Now(),
}
err = collection.Update(bson.M{"name": "Alice"}, user)
if err != nil {
    panic(err)
}

err = collection.Remove(bson.M{"name": "Alice"})
if err != nil {
    panic(err)
}

Among them, bson.M is a type in the mgo package, used for description Documents in MongoDB. In the Update and Remove methods, we can use bson.M to specify updated and deleted documents.

5. Summary

This article introduces how to use MongoDB in Go language. We first install MongoDB and use the mgo package to connect to the database. Then, we use the Insert and Find methods of the mgo package to insert and query documents in MongoDB. Finally, we covered how to use the Update and Remove methods to update and delete documents. By studying this article, you can master the basic methods of using MongoDB in Go language.

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