Golang's tutorial Accessing a relational database using docker

This project recreates the official Golang's tutorial Accessing a relational database using docker, so there is no need to install either Go or MySQL.

Downloading and installing docker

The goal of this tutorial is to replicate the Golang's tutorial but using docker, therefore you must first download and install it.

Set up the files

You can clone this repo or manually download all its files to your computer.

git clone https://github.com/carlos-medina/database-access-with-docker.git

Set up a database

In the .env file, we have the variable MYSQL_ROOT_PASSWORD. Its value is required to for both our application and our client to access the database.

MYSQL_ROOT_PASSWORD="admin"

In the compose.yaml file, regarding our database, we have two important information: services:db and networks:mysql-net:

services:
  db:
    image: mysql:8.0
    container_name: some-mysql
    env_file: .env
    ports:
      - 3306:3306
    networks:
      - mysql-net

networks:
  mysql-net:
    driver: bridge
    name: mysql-net

In db, we assign which mysql image from dockerhub will be used, the container name, the path to the .env file so it can get the variable MYSQL_ROOT_PASSWORD, which port is going to be exposed and which network the container is going to be connected to. It is important not to use the default docker's bridge network because docker's built-in DNS does not apply to this network.

In mysql-net we assing which driver will be used and the name of the network, which is the same used by our database.

Finally, we can head to a terminal and run our database:

docker compose up db

In a second terminal, we will create a container for the MySQL client:

docker run -it --network mysql-net --rm --name mysql-client mysql:8.0 mysql -hsome-mysql -uroot -p

In the container's terminal, we type the password atributed to the value MYSQL_ROOT_PASSWORD in our .env file, which is admin.

In a third terminal, we will copy the file create-table.sql to our database container:

docker cp ./create-tables.sql mysql-client:/create-tables.sql

In mysql-client's container terminal, we execute the following commands to 1. create the database 2. use it 3. execute the SQL commands from the copyied file and 4. check if the table was successfully created with the given data:

create database recordings;
use recordings;
source /create-tables.sql;
select * from album;

Run the code

In the .env file, we also have the variables DBUSER and DBPASS. Their value is required to for our application to access the database.

DBUSER="root"
DBPASS="admin"

In the compose.yaml file, regarding our application, besides networks that was already covered, we also have services:app:

services:
  app:
    image: golang:1.21.0-alpine3.18
    container_name: go-app
    working_dir: /usr/src/app
    volumes:
      - .:/usr/src/app
    command: go run ./main.go
    env_file: .env
    networks:
      - mysql-net

In app, we assign which go image from dockerhub will be used, the container name, from which directory the command will be executed, which files will be copied from the host to the container, which command will be executed, the path to the .env file and which network the container is going to be connected to.

Before running the app, there is only one change that you might do the the file main.go: On line 27, we have the struct key Addr and its value. If your some-mysql container's IP Address is different than 172.19.0.2:3306, you have to change it to its correct value. In order for you to find its value, you can inspect it using the command docker inspect:

docker inspect some-mysql | grep IPAddress

If your container's IP Adress is, for instance, 172.28.0.2, change the line 27 to

Addr: "172.19.0.2:3306",

from

Addr: "172.28.0.2:3306",

After the adjustments, run the command below in a terminal:

docker compose up app

You should see the following result:

[+] Running 1/0
 ✔ Container go-app  Created                                                                                                                                                                     0.1s 
Attaching to go-app
go-app  | go: downloading github.com/go-sql-driver/mysql v1.7.1
go-app  | Connected!
go-app  | Albums found: [{1 Blue Train John Coltrane 56.99} {2 Giant Steps John Coltrane 63.99}]
go-app  | Album found: {2 Giant Steps John Coltrane 63.99}
go-app  | ID of added album: 5
go-app exited with code 0