nginx: [emerg] mkdir() "/var/lib/nginx/tmp/client_body" failed (13: Permission denied)

I am currently running into a problem trying to set up a new user rather than using root in my docker file. The image builds fine, however when I run the container I get the following error: nginx: [emerg] mkdir() "/var/lib/nginx/tmp/client_body" failed (13: Permission denied)

Below is my dockerfile. I am using redhat UBi image build my dockerfile :

USER root
RUN microdnf --setopt=tsflags=nodocs install -y nginx procps shadow-utils net-tools ca-certificates dirmngr gnupg wget vim
            && microdnf clean all 
            && rpm -q procps-ng

ENV NGINX_USER="api-gatway" 
    NGINXR_UID="8987" 
    NGINX_GROUP="api-gatway" 
    NGINX_GID="8987"     

RUN set -ex; 
  groupadd -r --gid "$NGINX_GID" "$NGINX_GROUP"; 
  useradd -r --uid "$NGINXR_UID" --gid "$NGINX_GID" "$NGINX_USER" 


COPY nginx.conf /etc/nginx/nginx.conf


#To start up NGINX 
EXPOSE 80
RUN mkdir -p /var/lib/nginx/
RUN mkdir -p /var/log/nginx/

RUN mkdir -p /var/lib/nginx/tmp/

# chown owner-user:owner-group directory 

RUN chmod 755  api-gatway:api-gatway /var/lib/nginx/
RUN chmod 755  api-gatway:api-gatway /var/log/nginx/

EXPOSE 80
USER api-gatway
CMD ["nginx", "-g", "daemon off;"]

Any ideas why this is still not working?

Source: Docker Questions