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.

A shell script that invokes perl to set an environment variable used by Go. Some days I feel like there is a lot of duct tape involved in these applications.

Yeah, I'd also go with cgroups... but... You need to know if it's cgroups v1 or v2, where this filesystem is mounted, how to find your own process. Also, there's this hierarchical stuff going on there... also this can change dynamically while your program is running...