vim-dap is a Vim plugin for integrating with the Debug Adapter Protocol. to provide full debugger functionality for Vim. Unlike other debugger plugins, it doesn't attempt to replicate the user interface of an IDE; instead, interaction with the debugger happens in the terminal, through a fully readline-enabled debugger console:

Neovim's LSP API appears to still be in flux, so if something isn't working, the first thing to try would be to upgrade to the latest Neovim release.

This plugin is intended to be as configuration-free as possible, but this section will detail existing language support and their requirements.

Java requires you to be running the eclipse.jdt.ls language server with java-debug installed. The dap#run() method requires you to be using either Neovim with native LSP support, vim-lsp or LanguageClient-neovim as your client, but dap#connect() can be called manually to connect to the debug adapter if it's already running.

In order to run the language server with debug support, you will need to initialize the server with the path of the debug jar bundle. An example using settings.json:

{
  "initializationOptions": {
    "bundles": ["/path/to/java-debug.jar"]
  }
}

You will also need to add all of the jars included in the server extension for vscode-java-test. The easiest way to do that is to download it from the VSCode Marketplace:

https://vscjava.gallery.vsassets.io/_apis/public/gallery/publisher/vscjava/extension/vscode-java-test/${version}/assetbyname/Microsoft.VisualStudio.Services.VSIXPackage

The debug settings can be customized by defining either a .vim/launch.json or .vscode/launch.json file, i.e.

{
  "javaHome": "/usr/lib/jvm/java-11-openjdk-amd64"
}

To make it easier to run Java tests, I recommend adding something like this to your .vimrc. With this in place, you can use \rb to run all tests in the current file, \rf to only run the test which your cursor is in, and \rl to re-run the most recent test.

au filetype java nmap <Leader>rb :call dap#lang#java#run_test_class()<cr>
au filetype java nmap <Leader>rf :call dap#lang#java#run_test_method()<cr>
au filetype java nmap <Leader>rl :call dap#run_last()<cr>

First, make sure that you have Delve installed and that dlv is available on your PATH.

Second, the debug adapter for Go is implemented as part of vscode-go, so your system must have Node available in order for it to run (womp womp). It will be automatically downloaded on first use.