headless multiclient should exit when process dies

[briandealwis]

1. What version of Delve are you using (dlv version)?

1.2.0 (from HEAD)

2. What version of Go are you using? (go version)?

go version go1.12 darwin/amd64

4. What did you do?

Terminal 1:

$ dlv debug --headless --accept-multiclient ./_fixtures/buildtest/
API server listening at: 127.0.0.1:57699
debugserver-@(#)PROGRAM:LLDB  PROJECT:lldb-1100.0.25..3
 for x86_64.
Got a connection, launched process /Users/bsd/go/src/github.com/go-delve/delve/debug (pid = 15033).

Now from Terminal 2, we connect and continue the process (dlv connect --init <(echo continue) :57699). We see a message saying that the process has existed with status 0.

In Terminal 1, we see additional output:

hello world!
Exiting.

But the headless dlv process now never exits. We can connect to it repeatedly (dlv connect :57699), but the dlv client never prompts to kill the target and the headless dlv process never exits. The dlv debug appears to be hung.

5. What did you expect to see?

Exiting the dlv connect instance should have prompted whether to kill the target.

If I instead debug a simple web app that just waits (http.ListenAndServe(":8080", nil)), a dlv connect followed by an exit prompts whether I'd like to kill the target instance.

6. What did you see instead?

The dlv debug process Is still alive. Which I guess makes sense so that a user can restart?