build spring boot (mvnw) with docker can not use cache

Question

Spring Boot Docker Experimental Features Docker 18.06 comes with some “experimental” features, including a way to cache build dependencies. To switch them on, you need a flag in the daemon (dockerd) and an environment variable when you run the client. With the experimental features, you get different output on the console, but you can see that a Maven build now only takes a few seconds instead of minutes, provided the cache is warm.

my dockerfile can not use cache.

dockerfile

# syntax=docker/dockerfile:experimental
FROM openjdk:8-jdk-alpine as build
WORKDIR /workspace/app

COPY mvnw .
COPY .mvn .mvn
COPY pom.xml .
COPY src src

RUN --mount=type=cache,target=/root/.m2 ./mvnw install -DskipTests -s .mvn/wrapper/settings.xml
RUN mkdir -p target/extracted && java -Djarmode=layertools -jar target/*.jar extract --destination target/extracted

FROM openjdk:8-jre-alpine
ENV TZ Asia/Shanghai
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring

ARG EXTRACTED=/workspace/app/target/extracted
ARG JAVA_OPTS="-Xmx100m -Xms100m"

COPY --from=build ${EXTRACTED}/dependencies/ ./
COPY --from=build ${EXTRACTED}/spring-boot-loader/ ./
COPY --from=build ${EXTRACTED}/snapshot-dependencies/ ./
COPY --from=build ${EXTRACTED}/application/ ./

ENTRYPOINT ["sh", "-c","java ${JAVA_OPTS} org.springframework.boot.loader.JarLauncher"]

run shell

DOCKER_BUILDKIT=1 docker build -t org/spring-boot .

every time use many minutes