Dockerfile

FROM alpine:3.12.1

RUN apk update && \
    apk upgrade && \
    apk add --no-cache \
    curl \
    git \
    neovim \
    && \
    rm -rf /var/cache/apk/*

RUN curl -sf https://raw.githubusercontent.com/Shougo/dein.vim/master/bin/installer.sh \
    | sh -s /root/.cache/dein

RUN mkdir -p /root/.config/nvim
ADD init.vim /root/.config/nvim

CMD nvim -c "call dein#install()" -c "q" && nvim

init.vim

let s:dein_dir = expand('/root/.cache/dein')
let s:dein_repo_dir = s:dein_dir . '/repos/github.com/Shougo/dein.vim'
execute 'set rtp+=' . s:dein_repo_dir

if dein#load_state(s:dein_dir)
    call dein#begin(s:dein_dir)

    call dein#add('Shougo/dein.vim')
    call dein#add('sheerun/vim-polyglot')
    call dein#add('fatih/vim-go')

    call dein#end()
    call dein#save_state()
endif

message.txt

Error detected while processing /root/.cache/dein/.cache/init.vim/.dein/ftdetect/ftdetect.vim:
line 3598:
E121: Undefined variable: s:cpo_save
E15: Invalid expression: s:cpo_save
line 3599:
E108: No such variable: "s:cpo_save"
Press ENTER or type command to continue