$ cat os/signal/signal_linux_test.go 
// +build linux

package signal

import (
        "os"
        "syscall"
        "testing"
        "time"
)

const prSetKeepCaps = 8

func TestAllThreadsSyscallSignals(t *testing.T) {
        if _, _, err := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, prSetKeepCaps, 0, 0); err == syscall.ENOTSUP {
                t.Skip("AllThreadsSyscall disabled with cgo")
        }

        sig := make(chan os.Signal, 1)
        Notify(sig, os.Interrupt)

        for i := 0; i <= 100; i++ {
                if _, _, errno := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, prSetKeepCaps, uintptr(i&1), 0); errno != 0 {
                        t.Fatalf("[%d] failed to set KEEP_CAPS=%d: %v", i, i&1, errno)
                }
        }

        select {
        case <-time.After(10 * time.Millisecond):
        case <-sig:
                t.Fatal("unexpected signal")
        }
        Stop(sig)
        close(sig)
}

$ CGO_ENABLED=0 ../bin/go test -c os/signal
$ ./signal.test -test.v=1

$ ./signal.test -test.v=1
=== RUN   TestAllThreadsSyscallSignals
--- PASS: TestAllThreadsSyscallSignals (0.02s)
=== RUN   TestSignal
    signal_test.go:116: sighup...
    signal_test.go:127: sigwinch...
    signal_test.go:134: sighup...
    signal_test.go:137: sighup...
--- PASS: TestSignal (0.00s)
=== RUN   TestStress
<...all good beyond here...>

$ ./signal.test -test.v=1
=== RUN   TestAllThreadsSyscallSignals
<...hangs here...>