child_process.spawn sh not killable

Comming from here:
darkguy2008/parallelshell#22

(btw: Usecase for #1009)

Everytime I need to spawn a process I do it like this

if (process.platform === 'win32') {
    sh = 'cmd';
    shFlag = '/c';
} else {
    sh = 'sh';
    shFlag = '-c';
}
var child = spawn(sh,[shFlag,cmd], {
  cwd: process.cwd,
  env: process.env,
  stdio: ['pipe', process.stdout, process.stderr]
})

The problem: child is unkillable on unix.
Example in coffee-script:

spawn = require("child_process").spawn
child = spawn "sh", ["-c", "node -e 'setTimeout(function(){},10000);'"]
child.on "close", process.exit
child.kill()
child.kill("SIGINT")
child.kill("SIGTERM")
child.kill("SIGHUP")
spawn "sh",["-c","kill -TERM "+child.pid]
spawn "sh",["-c","kill -INT "+child.pid]
spawn "sh",["-c","kill -HUP "+child.pid]

(on windows it works fine with sh replaced by cmd)
Even when I exit the process with process.exit(), the child stays alive.

Workaround I found:

spawn = require("child_process").spawn
child = spawn "sh", ["-c", "node -e 'setTimeout(function(){},10000);'"], detached: true
child.on "close", process.exit
spawn "sh",["-c","kill -INT -"+child.pid]

Killing by pgid works, by pid works not. Sending ^C from console works also, I assume it uses pgid always.