Programmatically exec into docker container - bash

Question

I would like to write a program that allows the user to choose a running docker container which they can be given an interactive shell to. The flow of the program I would like to have is roughly the following:
user runs program from bash - ./my_program
user is given an
interactive cli they can use to choose which docker container to
exec into
when user chooses container, something like docker exec -it <CONTAINER_ID> bash is run from my_program, my_program exits, and the user is transferred into a shell session of the docker container as if they had manually run docker exec -it <CONTAINER_ID> bash
I'm trying this from golang with the following code:
rv, err := exec.Command("docker", "exec", "-it", containerId, "bash").Output()
log.Infof("RV: %v", rv)
if err != nil {
log.Errorf("Error exec-ing into container: %s", err)
}
and see the following output:
RV: []
Error exec-ing into container: exit status 1
I'm trying with err := exec.Command("docker", "exec", "-it", containerId, "bash").Run() as well and see the same error.
How might I go about creating a program like this or debugging what's currently happening?

Answer 1

Since you are launching your docker exec in interactive mode (-i) and with a tty (-t) the exec.Command needs to be provided a means for the user to send input/receive output from the tty.
To tie the cmd's stdin/stdout directly to your go process:
cmd := exec.Command("docker", "exec", "-it", containerId, "bash")
cmd.Stdin = os.Stdin
cmd.Stdout = os.Stdout
err := cmd.Run()
if err != nil {
panic(err)
}
// reached once user types `exit` from the bash shell
fmt.Println("Docker: bash console ended successfully")