为什么无法在dockerfile中加载环境变量？

Question

这是我的dockerfile。环境变量无法识别。
但是，硬编码的环境变量已被成功识别。成功识别出“ DOMAIN”或“ NOTICE_FILE_PATH”之类的

。

MAINTAINER JeongWooYeong(wjd030811@gmail.com)

ENV SECRET_KEY_BASE $SECRET_KEY_BASE
ENV SCARFS_PASSWORD $SCARFS_PASSWORD
ENV API_KEY $API_KEY
ENV DOMAIN dsm-scarfs.hs.kr
ENV NOTICE_FILE_PATH /home/ubuntu/scarfs/storage/notice_file
ENV EXCEL_FILE_PATH /home/ubuntu/scarfs/storage/excel_file
ENV SINGLE_FILE_PATH /home/ubuntu/scarfs/storage/single_file
ENV MULTI_FILE_PATH /home/ubuntu/scarfs/storage/multi_file
ENV SCARFS_DB $SCARFS_DB

RUN apt-get update && \
    apt-get install -y \
    default-libmysqlclient-dev \
    nodejs

RUN gem install bundler

COPY . .
WORKDIR .

RUN bundle install

EXPOSE 3000
VOLUME [".storage", "/home/ubuntu/T-bone"]
RUN  ["bundle", "exec", "unicorn", "-E", "production", "-c", "config/unicorn.rb"]

并导致以下错误：

ArgumentError: `secret_key_base` for production environment must be a type of String`

我该怎么办？