Fast outside ShinyProxy

I have docker container which runs and initiates quickly outside shiny proxy. However it takes 20-30 seconds to load within shiny proxy. ShinyProxy is running in the container. It is using port 3838 outside shinyproxy. In shiny proxt it is using port 8080. Any thought on fixing it up.

Dockerfile

FROM java:8
    RUN mkdir -p /opt/shinyproxy/
    RUN wget https://www.shinyproxy.io/downloads/shinyproxy-2.3.0.jar -O /opt/shinyproxy/shinyproxy.jar
    COPY application.yml /opt/shinyproxy/application.yml
    RUN mkdir /opt/shinyproxy/templates
    ADD templates /opt/shinyproxy/templates

    WORKDIR /opt/shinyproxy/
    CMD ["java", "-jar", "/opt/shinyproxy/shinyproxy.jar"]