how to execute and get the result from interactive command in go?

Question

func main() {

    //r, w := io.Pipe()
    //r1, w1 := io.Pipe()
    cmd := exec.Command("tr", "a-z", "A-Z")
    in, _ := cmd.StdinPipe()
    out, _ := cmd.StdoutPipe()
    go func() {
        fmt.Fprintf(in, "bbbb\n")
        fmt.Fprintf(in, "ccccc\n")
    }()
    go func() {
        scanner := bufio.NewScanner(out)
        for scanner.Scan() {
            fmt.Printf("data is %q \n", scanner.Text()) //it print nothing
        }
    }()
    cmd.Start()
    cmd.Wait()
}

here is my code, I want to run an interactive command and get the result. and not to stop the command process, I wish it can always run.

I try set Stdout to system, I will print the result. but I can't get it in code.

cmd.Stdout = os.Stdout

I try close output, but the application stop, but I hope it can always run.

go func() {
        fmt.Fprintf(in, "bbbb\n")
        fmt.Fprintf(in, "ccccc\n")
        in.Close()
}()