Go CLI を使用してリモート マシンでコマンドを実行するにはどうすればよいですか?

func remoteRun(user, addr, privateKey, cmd string) (string, error) {
    key, err := ssh.ParsePrivateKey([]byte(privateKey))
    if err != nil {
        return "", err
    }

    config := &ssh.ClientConfig{
        User: user,
        HostKeyCallback: ssh.InsecureIgnoreHostKey(),
        Auth: []ssh.AuthMethod{
            ssh.PublicKeys(key),
        },
    }

    client, err := ssh.Dial("tcp", net.JoinHostPort(addr, "22"), config)
    if err != nil {
        return "", err
    }

    session, err := client.NewSession()
    if err != nil {
        return "", err
    }
    defer session.Close()

    var b bytes.Buffer
    session.Stdout = &b
    err = session.Run(cmd)
    return b.String(), err
}

bastionOutput, err := remoteRun("user", "bastion-addr", "key", "ssh user@target-addr -p 22")
if err != nil {
    // Handle error
}
targetOutput, err := remoteRun("user", "target-addr", "key", "command-on-target")
if err != nil {
    // Handle error
}