Used the mounted path as the GOPATH

Dockerfile

@@ -13,19 +13,20 @@ RUN apt-get update && apt-get install -y \
     rm -rf /var/lib/apt/lists/*
 
 RUN export uid=1000 gid=1000 && \
-    mkdir -p /home/ubuntu && \
+    mkdir -p /home/ubuntu && mkdir /workspace && \
     echo "ubuntu:x:${uid}:${gid}:Developer,,,:/home/ubuntu:/bin/bash" >> /etc/passwd && \
     echo "ubuntu:x:${uid}:" >> /etc/group && \
     echo "ubuntu ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/ubuntu && \
     chmod 0440 /etc/sudoers.d/ubuntu && \
     chown ${uid}:${gid} -R /home/ubuntu
 
 ENV HOME /home/ubuntu
+ENV WORKSPACE /workspace
 ENV GOROOT "/usr/local/go"
-ENV GOPATH ${HOME}
+ENV GOPATH ${WORKSPACE}
 ENV PATH "$PATH:$GOPATH/bin:$GOROOT/bin"
 
-WORKDIR ${HOME}
+WORKDIR ${WORKSPACE}
 
 RUN wget --quiet https://dl.google.com/go/go1.15.3.linux-amd64.tar.gz \
 && tar -xf go1.15.3.linux-amd64.tar.gz \
@@ -34,7 +35,6 @@ RUN wget --quiet https://dl.google.com/go/go1.15.3.linux-amd64.tar.gz \
 ENV DRIVER_VERSION ${DRIVER_VERSION}
 ENV MONGODB_URI ${MONGODB_URI}
 
-RUN mkdir -p ${HOME}/go && mkdir /workspace
 COPY ./go/getstarted.go ${HOME}/go/getstarted.go
 COPY ./go/go.mod ${HOME}/go/go.mod