Ruby on Rails: How to work with RDS MySQL instance locally - ruby-on-rails

Question

Environment
Rails version: 6.0.0.rc2
Ruby version: ruby 2.6.3p62 (2019-04-16 revision 67580)
RDS MySql: Ver 8.0.15
Problem
I am trying to connect my RDS MySQL8 instance to my local Ruby on Rails application for testing purposes. My app is working fine with a local version of MySQL8.0.12 with the mysql2 gem.
When I use the RDS DB's details and I run bin/rake db:[anything] VERBOSE=true in the command line, it just hangs without giving ANY information on why it isn't working. Output below.
This is purely to test the db I want to use for a staging environment.
I've connected to the RDS DB from the command line and DBeaver from my local machine, and I've been able to create new tables, so security groups should be ok.
I've used the db connection test script below to ensure that ActiveRecord::Base.connected is true
Connected, initiated, migrated and seeded a local mysql db just in case.
database.yml
#
default: &default
adapter: mysql2
encoding: utf8mb4
pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
host: [aws_rds_host_url]
username: <%= ENV.fetch("DB_USERNAME") %>
password: <%= ENV.fetch("DB_PASSWORD") %>
database: db_name
test script found somewhere on stackoverflow (returns "CONNECTED!")
require './config/environment.rb' # Assuming the script is located in the root of the rails app
begin
ActiveRecord::Base.establish_connection # Establishes connection
ActiveRecord::Base.connection # Calls connection object
puts "CONNECTED!" if ActiveRecord::Base.connected?
puts "NOT CONNECTED!" unless ActiveRecord::Base.connected?
rescue StandardError => e
puts e
puts "rescue:: NOT CONNECTED!"
end
Running bin/rake db:create VERBOSE=true || bin/rake db:migrate VERBOSE=true (or anything rake db:) keeps hanging, tried for more than an hour. It does not make any changes to the DB. Stopped with cmd+C it just returns:
bin/rake db:create VERBOSE=true
^CTraceback (most recent call last):
14: from bin/rake:3:in `<main>'
13: from bin/rake:3:in `load'
12: from [home]/[project dir]/bin/spring:16:in `<top (required)>'
11: from [home]/.rbenv/versions/2.6.3/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
10: from [home]/.rbenv/versions/2.6.3/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
9: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/binstub.rb:11:in `<top (required)>'
8: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/binstub.rb:11:in `load'
7: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/bin/spring:49:in `<top (required)>'
6: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/client.rb:30:in `run'
5: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/client/command.rb:7:in `call'
4: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/client/run.rb:35:in `call'
3: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/client/run.rb:42:in `warm_run'
2: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/client/run.rb:62:in `run'
1: from [home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/client/run.rb:117:in `verify_server_version'
[home]/[project dir]/vendor/bundle/ruby/2.6.0/gems/spring-2.1.0/lib/spring/client/run.rb:117:in `gets': Interrupt