add ustc pypi mirror

Dockerfile

@@ -23,7 +23,7 @@ WORKDIR /code
 COPY --from=requirements-stage /tmp/requirements.txt /code/requirements.txt
 
 #
-RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt
+RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt -i https://pypi.tuna.tsinghua.edu.cn/simple
 
 #
 COPY ./app /code/app