Support specific version of yarn.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

docker-compose.yml

@@ -28,6 +28,7 @@ services:
                 - PUID=1000
                 - PGID=1000
                 - NODE_VERSION=stable
+                - YARN_VERSION=latest
                 - TZ=UTC
         volumes_from:
             - applications

workspace/Dockerfile

@@ -189,10 +189,16 @@ USER laradock
 
 ARG INSTALL_YARN=false
 ENV INSTALL_YARN ${INSTALL_YARN}
+ARG YARN_VERSION=latest
+ENV YARN_VERSION ${YARN_VERSION}
 
 RUN if [ ${INSTALL_YARN} = true ]; then \
     [ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh" && \
-    curl -o- -L https://yarnpkg.com/install.sh | bash && \
+    if [ ${YARN_VERSION} = "latest" ]; then \
+        curl -o- -L https://yarnpkg.com/install.sh | bash; \
+    else \
+        curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version ${YARN_VERSION}; \
+    fi && \
     echo "" >> ~/.bashrc && \
     echo 'export PATH="$HOME/.yarn/bin:$PATH"' >> ~/.bashrc \
 ;fi