A wrapper around `exec.Command(...).Output()` to execute external commands / binaries with support for cancellation signals via channels (i.e. terminate the running process).

command.go

package main

import (
	"errors"
	"log"
	"os/exec"
)

var (
	ErrCmdCancelled = errors.New("command cancelled")
)

func Execute(command []string, done <-chan struct{}) ([]byte, error) {
	cmd := exec.Command(command[0], command[1:]...)
	outCh := make(chan []byte, 1)
	errCh := make(chan error, 1)

	go func() {
		out, err := cmd.Output()
		if err != nil {
			errCh <- err
			return
		}
		outCh <- out
	}()

	select {
	case out := <-outCh:
		close(errCh)
		return out, nil
	case err := <-errCh:
		close(outCh)
		return nil, err
	case <-done:
		log.Println("exiting")
		// if (cmd.ProcessState == nil || cmd.ProcessState.Exited() == false) && cmd.Process != nil {
		if cmd.Process != nil {
			if err := cmd.Process.Kill(); err != nil {
				return nil, err
			}
		}
		return nil, ErrCmdCancelled
	}
}

Pro-tip: use a Context instead!