This plugin is the first plugin i have ever made that has a config file! When a player joins your server this plugin will wait 10 game ticks and then give the player a firework rocket that they can not drop nor move around in their inventory. They can right click while holding it and then access a speed settings gui. Using that speed settings gui they can change their speed anywhere from 1 to 5. They will then get the speed effect that will also be saved inside the config.yml every tick for 2 game ticks if they are in the world that you specified in the config.yml. This plugin is made for minecraft server version paper 1.17.1 and tested on minecraft server version paper 1.18.2.
The default config.yml can be found here.
Below you will find a download to the plugin.jar file.