FWIW, there is a GDScript syntax highlighter and completion plugin for vim [0], and there was also a GSOC project to add language server support for GDScript [1]. I don't know the exact status of the PRs besides that some parts of it haven't been merged yet, but some did apparently make it into Godot 3.2. I'm sure testing and bugfixes would be appreciated.

[0] https://github.com/calviken/vim-gdscript3

[1] https://godotengine.org/article/gsoc-2019-progress-report-1-...