This is not very robust. You probably should use the cgroup cpu limits where present, since `docker --cpus` uses a different way to set quota:

    if [[ -e /sys/fs/cgroup/cpu/cpu.cfs_quota_us ]] && [[ -e /sys/fs/cgroup/cpu/cpu.cfs_period_us ]]; then
        GOMAXPROCS=$(perl -e 'use POSIX; printf "%d\n", ceil($ARGV[0] / $ARGV[1])' "$(cat /sys/fs/cgroup/cpu/cpu.cfs_quota_us)" "$(cat /sys/fs/cgroup/cpu/cpu.cfs_period_us)")
    else
        GOMAXPROCS=$(nproc)
    fi
    export GOMAXPROCS

This follows from how `docker --cpus` works (https://docs.docker.com/config/containers/resource_constrain...), as well as https://stackoverflow.com/a/65554131/207384 to get the /sys paths to read from.

Or use https://github.com/uber-go/automaxprocs, which is very comprehensive, but is a bunch of code for what should be a simple task.