laravel-echo-server add change source

laravel-echo-server/Dockerfile

@@ -7,6 +7,14 @@ WORKDIR /usr/src/app
 # Install app dependencies
 COPY package.json /usr/src/app/
 
+# If you're in China, or you need to change sources, will be set CHANGE_SOURCE to true in .env.
+
+ARG CHANGE_SOURCE=false
+RUN if [ ${CHANGE_SOURCE} = true ]; then \
+    # Change application source from dl-cdn.alpinelinux.org to aliyun source
+    sed -i 's/dl-cdn.alpinelinux.org/mirrors.aliyun.com/' /etc/apk/repositories \
+;fi
+
 RUN apk add --update \
     python \
     python-dev \