How to use modules from my Ruby gem in my Sinatra app - activerecord

Question

I am working on an unpublished gem, which is working correctly in Rails. It has a module that needs to be included inside of ActiveRecord::Base classes.
My Sinatra app looks like this:
# app.rb
require 'rubygems'
require 'sinatra'
require 'sinatra/activerecord'
set :database, "sqlite3:project-name.sqlite3"
get '/' do
#users = User.all
erb :index
end
class User < ActiveRecord::Base
end
My gem file looks like this:
source 'https://rubygems.org'
gem 'activerecord'
gem 'sinatra-activerecord'
gem 'sqlite3'
gem 'rake'
gem "my_module", path: "../my_module"
My Gemfile.lock looks like this:
PATH
remote: ../my_module
specs:
my_module (1.49.0)
activerecord (>= 4.2)
GEM
remote: https://rubygems.org/
specs:
activemodel (6.0.2.1)
activesupport (= 6.0.2.1)
activerecord (6.0.2.1)
activemodel (= 6.0.2.1)
activesupport (= 6.0.2.1)
activesupport (6.0.2.1)
concurrent-ruby (~> 1.0, >= 1.0.2)
i18n (>= 0.7, < 2)
minitest (~> 5.1)
tzinfo (~> 1.1)
zeitwerk (~> 2.2)
concurrent-ruby (1.1.5)
i18n (1.7.0)
concurrent-ruby (~> 1.0)
minitest (5.13.0)
mustermann (1.0.3)
rack (2.0.8)
rack-protection (2.0.7)
rack
rake (13.0.1)
sinatra (2.0.7)
mustermann (~> 1.0)
rack (~> 2.0)
rack-protection (= 2.0.7)
tilt (~> 2.0)
sinatra-activerecord (2.0.14)
activerecord (>= 3.2)
sinatra (>= 1.0)
sqlite3 (1.4.2)
thread_safe (0.3.6)
tilt (2.0.10)
tzinfo (1.2.5)
thread_safe (~> 0.1)
zeitwerk (2.2.2)
PLATFORMS
ruby
DEPENDENCIES
activerecord
rake
my_module!
sinatra-activerecord
sqlite3
BUNDLED WITH
2.0.2
And if I add the module manually it works fine:
# app.rb
require 'rubygems'
require 'sinatra'
require 'sinatra/activerecord'
set :database, "sqlite3:project-name.sqlite3"
get '/' do
#users = User.all
erb :index
end
module MyModule
extend ActiveSupport::Concern
class_methods do
#something here
end
end
class User < ActiveRecord::Base
include MyModule
end
I expect to be able to do:
# app.rb
require 'rubygems'
require 'sinatra'
require 'sinatra/activerecord'
require 'my_module'
set :database, "sqlite3:project-name.sqlite3"
get '/' do
#users = User.all
erb :index
end
class User < ActiveRecord::Base
include MyModule
end
I get the error
cannot load such file -- my_module (LoadError)
when I use the require statement or
uninitialized constant User::MyModule (NameError)
if I remove require.

Answer 1

It works if I use
bundle exec ruby app.rb
instead of
ruby app.rb