Terminating a Process Started with os/exec in Golang

Is there a way to terminate a process started with os.exec in Golang? For example (from http://golang.org/pkg/os/exec/#example_Cmd_Start),

cmd := exec.Command("sleep", "5")
err := cmd.Start()
if err != nil {
    log.Fatal(err)
}
log.Printf("Waiting for command to finish...")
err = cmd.Wait()
log.Printf("Command finished with error: %v", err)

Is there a way to terminate that process ahead of time, perhaps after 3 seconds?

Run and terminate an exec.Process:

// Start a process:
cmd := exec.Command("sleep", "5")
if err := cmd.Start(); err != nil {
    log.Fatal(err)
}

// Kill it:
if err := cmd.Process.Kill(); err != nil {
    log.Fatal("failed to kill process: ", err)
}

Run and terminate an exec.Process after a timeout:

ctx, cancel := context.WithTimeout(context.Background(), 3 * time.Second)
defer cancel()

if err := exec.CommandContext(ctx, "sleep", "5").Run(); err != nil {
    // This will fail after 3 seconds. The 5 second sleep
    // will be interrupted.
}

See this example in the Go docs

Legacy

Before Go 1.7, we didn't have the context package and this answer was different.

Run and terminate an exec.Process after a timeout using channels and a goroutine:

// Start a process:
cmd := exec.Command("sleep", "5")
if err := cmd.Start(); err != nil {
    log.Fatal(err)
}

// Wait for the process to finish or kill it after a timeout (whichever happens first):
done := make(chan error, 1)
go func() {
    done <- cmd.Wait()
}()
select {
case <-time.After(3 * time.Second):
    if err := cmd.Process.Kill(); err != nil {
        log.Fatal("failed to kill process: ", err)
    }
    log.Println("process killed as timeout reached")
case err := <-done:
    if err != nil {
        log.Fatalf("process finished with error = %v", err)
    }
    log.Print("process finished successfully")
}

Either the process ends and its error (if any) is received through done or 3 seconds have passed and the program is killed before it's finished.

Stack Overflow Q#11886531, score: 170