fix race condition

Author: vadv

cmd/api.go

@@ -37,9 +37,15 @@ func Exec(L *lua.LState) int {
 	cmd.Stderr = &stderr
 	cmd.Stdout = &stdout
 
+	if err := cmd.Start(); err != nil {
+		L.Push(lua.LNil)
+		L.Push(lua.LString(err.Error()))
+		return 2
+	}
+
 	done := make(chan error)
 	go func() {
-		done <- cmd.Run()
+		done <- cmd.Wait()
 	}()
 
 	select {