How to get Lua code completion?

[StudentScripter]

The lua language server is checked and the plugin is active i just want to write simple scripts, but its useless without code completion is i don't see what i can use.

This is the basic hello world it works, but no code completion. How to enable it?

T = require'TextEditor'
editor = T.currentEditor()
cursor = editor:cursor()
cursor:insertText('-- Hello World!')

[StudentScripter]

There also seems no documentation at all. :(