How to Reliably Kill Child Processes in Go When a Timeout Occurs?

Killing Child Processes in Go: Resolving Timeout Issues

In the provided Go code snippet, despite setting a timeout of 2 seconds and attempting to terminate a child process with a signal, the process persists and "Done waiting" remains unprinted. This behavior suggests that the process remains active beyond the allotted time.

The root of this issue lies in the use of cmd.Process.Signal() to terminate the child process. It's important to note that this function only sends signals to the main process, not its children. To effectively terminate child processes, it is necessary to target the process group that contains the child process, which can be done using the following approach:

// First, create the command and set up its attributes
cmd := exec.Command( some_command )
cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}

// Then, start the command
cmd.Start()

// Next, obtain the process group ID of the child process
pgid, err := syscall.Getpgid(cmd.Process.Pid)
if err == nil {
    // If the process group ID is successfully obtained, terminate it
    syscall.Kill(-pgid, 15)  // note the minus sign
}

// Finally, wait for the command to complete
cmd.Wait()

By setting Setpgid to true in syscall.SysProcAttr, we instruct the OS to create a new process group for the child process, ensuring that signals sent to the parent process don't affect the child process. The minus sign in -pgid ensures that the signal is sent to all members of the process group, including any child processes.

This solution is platform-specific and may not work on all operating systems. However, it has been reported to work on OSX Yosemite and various Linux distributions, while its compatibility on Windows and BSD remains uncertain.

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