You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: proxy_linux.go
    path of file: ./repos/moby/libnetwork/portmapper
    
    the code of the file until where you have to start completion: package portmapper

import (
	"fmt"
	"io"
	"net"
	"os"
	"os/exec"
	"runtime"
	"strconv"
	"syscall"
	"time"
)

func newProxyCommand(proto string, hostIP net.IP, hostPort int, containerIP net.IP, containerPort int, proxyPath string) (userlandProxy, error) {
	if proxyPath == "" {
		return nil, fmt.Errorf("no path provided for userland-proxy binary")
	}

	return &proxyCommand{
		cmd: &exec.Cmd{
			Path: proxyPath,
			Args: []string{
				proxyPath,
				"-proto", proto,
				"-host-ip", hostIP.String(),
				"-host-port", strconv.Itoa(hostPort),
				"-container-ip", containerIP.String(),
				"-container-port", strconv.Itoa(containerPort),
			},
			SysProcAttr: &syscall.SysProcAttr{
				Pdeathsig: syscall.SIGTERM, // sen
    
func newProxyCommand(proto string, hostIP net.IP, hostPort int, containerIP net.IP, containerPort int, proxyPath string) (userlandProxy, error) {
	if proxyPath == "" {
		return nil, fmt.Errorf("no path provided for userland-proxy binary")
	}

	return &proxyCommand{
		cmd: &exec.Cmd{
			Path: proxyPath,
			Args: []string{
				proxyPath,
				"-proto", proto,
				"-host-ip", hostIP.String(),
				"-host-port", strconv.Itoa(hostPort),
				"-container-ip", containerIP.String(),
				"-container-port", strconv.Itoa(containerPort),
			},
			SysProcAttr: &syscall.SysProcAttr{
				Pdeathsig: syscall.SIGTERM, // send a sigterm to the proxy if the creating thread in the daemon process dies (https://go.dev/issue/27505)
			},
		},
		wait: make(chan error, 1),
	}, nil
}