可以透過給容器運行時的環境變數的方式，
在運行時給定不同的後端 API 網址，而不必在 build 階段。

Dockerfile:

# 基礎映像檔
FROM node:14-alpine

# 建立工作目錄
WORKDIR /app

# 複製應用程式到工作目錄
COPY . .

# 安裝 npm 套件
RUN npm install

# 定義環境變數，用於運行時給定 API 網址
ENV API_URL=""

# 運行應用程式
CMD ["npm", "start", "--", "--apiUrl=$API_URL"]

我們透過 -e 參數給定 API_URL 環境變數，並在運行應用程式時使用該變數，以達到不同環境使用不同後端 API 網址的目的。

運行容器範例:

docker run -e API_URL=http://api-server-A.com my-image-name

你好，我是使用 nginx 容器裡面的 envsubst 工具在容器啟動時替換，您可以參考看看。
參考 https://blog.miniasp.com/post/2018/08/22/Angular-nginx-reverse-proxy-and-Docker

Dockerfile

FROM nginx:${NGINX_VERSION}-alpine as prd
COPY --from=build /app/dist /usr/share/nginx/html
# 把 Nginx 模版複製到 Nginx 的設定檔目錄
COPY .docker/nginx.template /etc/nginx/conf.d/
# 利用 envsubst 將特定字串替換成指定文字
CMD envsubst '${BACKEND_URI}${FAB8F_URI}${WEATHER_8T_URI}' < /etc/nginx/conf.d/nginx.template > /etc/nginx/conf.d/default.conf && \
    exec nginx -g 'daemon off;'

nginx.template

server {
    listen 80;

    root  /usr/share/nginx/html;

    proxy_set_header Host $proxy_host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header x-forwarded-for  $remote_addr;
    proxy_set_header X-Forwarded-Host $server_name;

    # 這裡要指定 log，Nginx 才會寫入
    # 預設的 access.log 是空的
    access_log /var/log/nginx/frontend-access.log custom;
    error_log /var/log/nginx/frontend-error.log;

    # The dog.ceo domain is very slow that will lead nginx resolver not working.
    resolver 172.28.0.1 valid=30s ipv6=off;

    location ~/backend(.+)$ {
        proxy_pass ${BACKEND_URI}$1?$args;
        proxy_redirect off;
        proxy_set_header Host $proxy_host;
    }

    location ~/8f-amas(.+)$ {
        proxy_pass ${FAB8F_URI}$1?$args;
        proxy_redirect off;
        proxy_set_header Host $proxy_host;
        proxy_connect_timeout 10s;
        proxy_send_timeout 10s;
        proxy_read_timeout 10s;
    }

    location ~/8t-weather(.+)$ {
        proxy_pass ${WEATHER_8T_URI}$1?$args;
        proxy_redirect off;
        proxy_set_header Host $proxy_host;
        proxy_connect_timeout 90s;
        proxy_send_timeout 90s;
        proxy_read_timeout 90s;
        proxy_ignore_client_abort on;
    }
}

docker-compose.yml

service:
    frontend:
        build:
          context: ./frontend
          target: prd
        networks:
          net:
            ipv4_address: 172.28.0.2
        ports:
          - 80:80
        volumes:
          - nginx_log:/var/log/nginx
        environment:
          BACKEND_URI: http://172.28.0.3:3003
          FAB8F_URI: http://172.28.0.4:3050
          WEATHER_8T_URI: http://172.28.0.5:3090
          TZ: Asia/Taipei
        restart: on-failure:5