docker-compose up `require': 无法加载此类文件 -- pg (LoadError)

如何解决docker-compose up `require': 无法加载此类文件 -- pg (LoadError)

当我运行 docker-compose up 时，我收到了这个错误 bin/entrypoint:6:in `require': 无法加载这样的文件 -- pg (LoadError)，有人可以帮忙吗？谢谢

bin/入口点

#!/usr/bin/env ruby
# frozen_string_literal: true

require 'timeout'
require 'bundler/setup'
require 'pg'
...

docker 文件

ARG SERVER_ROOT=/srv/app
ARG RUBY_VERSION=2.6.6
ARG NODE_VERSION=12.18
ARG YARN_VERSION=1.22.4

FROM ruby:${RUBY_VERSION}-alpine AS gem
ARG SERVER_ROOT

RUN apk add --no-cache postgresql-dev build-base ca-certificates zlib-dev libressl-dev git

RUN mkdir -p ${SERVER_ROOT}
ADD Gemfile Gemfile.lock ${SERVER_ROOT}/

workdir ${SERVER_ROOT}
RUN gem install bundler:2.1.4 \
...

docker-compose

services:
  traefik:
    image: traefik:v2.2
    command:
      - "--providers.docker=true"
      - "--entrypoints.web.address=:9000"
    ports:
      - "9000:9000"
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock:ro"
    depends_on:
      - etm
  postgres:
    image: postgres:12
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      POSTGRES_DB: XXX
      POSTGRES_USER: XXX
      POSTGRES_PASSWORD: XXX
      ...