将cmd stdout和stderr作为字符串返回,而不是在golang中打印到控

cmd.Stdout = os.Stdout 
cmd.Stderr = os.Stderr

但我希望stdout和stderr作为字符串变量从runBashCommandAndKillIfTooSlow函数返回,而不立即打印到控制台.
怎么实现这个？

代码：

package main

import (
    "fmt"
    "log"
    "os"
    "os/exec"
    "time"
)

func main() {
    ok,outString,errString := runBashCommandAndKillIfTooSlow("ls -la",2000)
    fmt.Println("ok")
    fmt.Println(ok)
    fmt.Println("outString")
    fmt.Println(outString)
    fmt.Println("errString")
    fmt.Println(errString)
}

/*
run bash command and kill it if it works longer than "killInMilliSeconds" milliseconds
*/
func runBashCommandAndKillIfTooSlow(command string,killInMilliSeconds time.Duration) (okResult bool,stdout,stderr string) {
    fmt.Println("running bash command...")
    fmt.Println(command)
    cmd := exec.Command("sh","-c",command)

    cmd.Stdout = os.Stdout // cmd.Stdout -> stdout
    cmd.Stderr = os.Stderr // cmd.Stderr -> stderr

    okResult = true

    err := cmd.Start()
    log.Printf("Waiting for command to finish...")
    done := make(chan error,1)
    go func() {
        done <- cmd.Wait()
    }()
    select {
    case <-time.After(killInMilliSeconds * time.Millisecond):
        if err := cmd.Process.Kill(); err != nil {
            log.Fatal("failed to kill: ",err)
            okResult = false
        }
        <-done // allow goroutine to exit
        // log.Println("process killed")
    case err := <-done:

        if err != nil {
            log.Printf("process done with error = %v",err)
            okResult = false
        }
    }
    if err != nil {
        log.Fatal(err)
        okResult = false
    }
    return
}

顺便说一下,如果程序太慢(killInMilliSeconds参数),程序应该保留杀死bash命令的能力.