When I run rails: db: migrate, I get "Directly inheriting from ActiveRecord :: Migration is not supported."

About this article
When I execute "rails: db: migrate" in the flow of adding columns while creating my own application, "Directly inheriting from ActiveRecord :: Migration is not supported." Is displayed and an error occurs. It was a rudimentary mistake, but I posted it as a memorandum!

[environment] ・ Ruby 2.6.5, Rails 6.0.0 ・ MacOS

rake aborted!
StandardError: An error has occurred, all later migrations canceled:

Directly inheriting from ActiveRecord::Migration is not supported. Please specify the Rails release the migration was written for:

Upon investigating, the cause seemed to be that the migration file did not correspond to the rails version. ..

Add the rails version to the end of the first line of the target migration file.

class AddAttachmentImageToPosts < ActiveRecord::Migration[6.0] #←[6.0]Add
  def self.up
    change_table :posts do |t|
      t.attachment :image
    end
  end

  def self.down
    remove_attachment :posts, :image
  end
end

After that, I tried the following again to solve the problem.

$ rails db:migarate

Finally
I think that there are many cases where you get an error when you implement it, and you do not get the results you want. In such a case, let's calmly face the error sentence carefully!