Get it via the Toolbox App, download from the website, or use a snap package (for Ubuntu). Or, right in GoLand, select Automatically check updates for Early Access Program in Preferences / Settings | Appearance & Behavior | System Settings | Updates.
You can also use nightly builds based on the latest development code almost every day, if you don’t want to wait for the official announcements of EAP builds. Note they are available via the Toolbox App only.
For unused parameters, GoLand highlights its name and type if both can be removed, or only the name if the type is used for implementing a method specification.
In the latter case, the IDE now provides two quick-fixes for you to choose from: Delete parameter names or Rename to _. The same behavior is provided for functions that are used as a function type.