gosu error: failed switching to "root": operation not permitted

Question

When I use gosu ... it shows error info failed switching to "root": operation not permitted

Dockerfile

FROM python:3.10.2-alpine3.15
RUN apk update && apk add ca-certificates
# download gosu
# ....
ARG USER=ansibler
ARG GROUP=ansibler
ARG UID=1000
ARG GID=1000
RUN addgroup -g $GID $GROUP && adduser -u $UID -G $USER -D $USER && \
    echo 'ansibler ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
ENTRYPOINT [ "/tmp/entrypoint.sh" ]
CMD [ "/bin/bash" ]
USER $USER

in my entrypoint.sh, I wanna use command -> gosu root sed -i -e .... , After docker build -t, when i use docker run it that show the error as below -> error: failed switching to "root": operation not permitted