Getting started

Before you start, make sure you understand the concept or database migration and rollback.

Create new Go project and configure a database for it. Make sure that your database is supported here For the purpose of this tutorial let's create PostgreSQL database called example. Our user here is postgres, and host is localhost.

psql -h localhost -U postgres -w -c "create database example;"

When using Migrate CLI we need to pass to database URL. Let's export it to a variable for convienience:

export POSTGRESQL_URL=postgres://postgres:postgres@localhost:5432/example?sslmode=disable

sslmode=disable means that the connection with out database will not be encrypted. Enabling it is left as an exercise.

You can find further description of database URLs here.

Create migrations

Let's create table called users:

migrate create -ext sql -dir db/migrations create_users_table

If there were no errors, we should have two files available under db/migrations folder. Note the sql extension that we provided. In the .up.sql file we are going to create table:

CREATE TABLE users(
   user_id serial PRIMARY KEY,
   username VARCHAR (50) UNIQUE NOT NULL,
   password VARCHAR (50) NOT NULL,
   email VARCHAR (300) UNIQUE NOT NULL
);

And in the .down.sql we are going to delete it:

DROP TABLE users;

Run migrations

migrate -database ${POSTGRESQL_URL} -path db/migrations up

Let's check if the table was created properly by running psql example -c "\d users". The output you are supposed to see:

                                    Table "public.users"
  Column  |          Type          |                        Modifiers                        
----------+------------------------+---------------------------------------------------------
 user_id  | integer                | not null default nextval('users_user_id_seq'::regclass)
 username | character varying(50)  | not null
 password | character varying(50)  | not null
 email    | character varying(300) | not null
Indexes:
    "users_pkey" PRIMARY KEY, btree (user_id)
    "users_email_key" UNIQUE CONSTRAINT, btree (email)
    "users_username_key" UNIQUE CONSTRAINT, btree (username)

Great! Now let's check if rollback also works:

migrate -database ${POSTGRESQL_URL} -path db/migrations down

Make sure to check if your database changed as expected on rollback.

Before commiting your migrations: You should run your migrations, rollback them, and then run them again to see if migrations are working properly both ways. (e.g. if you created a table in a migration but rollback did not delete it, you will encounter an error when running the migration again) It's also worth checking your migrations in a separate, containerized environment. You can find some tools in the end of this tutorial.

Hint: Most probably you are going to use to the above commands often, it's worth putting them in a Makefile of your project.

Optional: Run migrations within your Go app

Here is a very simple app running migrations for the above configuration:

import (
	"log"

	"github.com/golang-migrate/migrate/v4"
	_ "github.com/golang-migrate/migrate/v4/database/postgres"
	_ "github.com/golang-migrate/migrate/v4/source/file"
)

func main() {
	m, err := migrate.New(
		"file://db/migrations",
		"postgres://postgres:postgres@localhost:5432/example?sslmode=disable")
	if err != nil {
		log.Fatal(err)
	}
	if err := m.Up(); err != nil {
		log.Fatal(err)
	}
}

You can find details here

Just add the code to your app and you're ready to go!

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Getting started

Create migrations

Run migrations

Optional: Run migrations within your Go app

Further reading:

3.8 KiB

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