cgroup in go

Dockerfile

FROM golang:alpine AS builder
RUN apk update && apk add --no-cache git
COPY hello.go hello.go
RUN go get -d -v
RUN go build -o /go/bin/hello
FROM scratch
COPY --from=builder /go/bin/hello /go/bin/hello
ENTRYPOINT ["/go/bin/hello"]

hello.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"

	_ "go.uber.org/automaxprocs"
)

func main() {
	files, err := ioutil.ReadDir("/sys/fs/cgroup")
	if err != nil {
		log.Fatal(err)
	}

	for _, f := range files {
		fmt.Println(f.Name())
	}
}

Seems to work as expected

$ docker run -it --rm --cpus=2 bbd1f832167e 
2020/03/13 16:18:42 maxprocs: Updating GOMAXPROCS=2: determined from CPU quota
blkio
cpu
cpu,cpuacct
cpuacct
cpuset
devices
freezer
hugetlb
memory
net_cls
net_cls,net_prio
net_prio
perf_event
pids
rdma
systemd

$ docker run -it --rm --cpus=3 bbd1f832167e 
2020/03/13 16:18:51 maxprocs: Updating GOMAXPROCS=3: determined from CPU quota
blkio
cpu
cpu,cpuacct
cpuacct
cpuset
devices
freezer
hugetlb
memory
net_cls
net_cls,net_prio
net_prio
perf_event
pids
rdma
systemd