Reduce building duration

Dockerfile

@@ -1,13 +1,13 @@
-FROM python:3.9 as builder
+FROM python:3.9-slim-buster as builder
 RUN apt-get update && apt-get install -y build-essential
 COPY requirements.txt .
 RUN pip install --user -r requirements.txt
 
-FROM python:3.9
+FROM python:3.9-slim-buster
 MAINTAINER iskoldt
 COPY --from=builder /root/.local /root/.local
 ENV PATH=/root/.local/bin:$PATH
-COPY . /app
 WORKDIR /app
+COPY ChuanhuChatbot.py .
 ENV my_api_key empty
 CMD ["python3", "-u", "ChuanhuChatbot.py", "2>&1", "|", "tee", "/var/log/application.log"]