From ef49aa7e080d85dd3b510de2408b82fc3e8e7668 Mon Sep 17 00:00:00 2001
From: James Shubin <james@shubin.ca>
Date: Fri, 30 Mar 2018 06:36:04 -0400
Subject: [PATCH] lang: Don't race with a ^C to the obj.lang calls

If we trigger a close, we must not run the LangClose before we've exited
from the loop, because that loop could race and run code which depends
on LangClose not having run first. So run the loop shutdown, then let
the wait group expire, before shutting down the lang.
---
 lang/gapi.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lang/gapi.go b/lang/gapi.go
index e450755d..353aaaaa 100644
--- a/lang/gapi.go
+++ b/lang/gapi.go
@@ -178,7 +178,10 @@ func (obj *GAPI) Next() chan gapi.Next {
 				Err:  fmt.Errorf("%s: GAPI is not initialized", Name),
 				Exit: true, // exit, b/c programming error?
 			}
-			ch <- next
+			select {
+			case ch <- next:
+			case <-obj.closeChan:
+			}
 			return
 		}
 		startChan := make(chan struct{}) // start signal
@@ -259,9 +262,9 @@ func (obj *GAPI) Close() error {
 	if !obj.initialized {
 		return fmt.Errorf("%s: GAPI is not initialized", Name)
 	}
-	obj.LangClose() // close lang, esp. if blocked in Stream() wait
 	close(obj.closeChan)
 	obj.wg.Wait()
+	obj.LangClose()         // close lang, esp. if blocked in Stream() wait
 	obj.initialized = false // closed = true
 	return nil
 }