From b51cd5406ac101b48f56ac0df4f0fedac4c65950 Mon Sep 17 00:00:00 2001
From: Chris Bednarski <banzaimonkey@gmail.com>
Date: Mon, 12 Oct 2015 18:12:22 -0700
Subject: [PATCH 1/2] Add explicit wait after Communicator.Download to make
 sure serveSingleCopy completes

---
 packer/rpc/communicator.go | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/packer/rpc/communicator.go b/packer/rpc/communicator.go
index abf841af8..525418ee2 100644
--- a/packer/rpc/communicator.go
+++ b/packer/rpc/communicator.go
@@ -2,11 +2,12 @@ package rpc
 
 import (
 	"encoding/gob"
-	"github.com/mitchellh/packer/packer"
 	"io"
 	"log"
 	"net/rpc"
 	"os"
+
+	"github.com/mitchellh/packer/packer"
 )
 
 // An implementation of packer.Communicator where the communicator is actually
@@ -137,7 +138,13 @@ func (c *communicator) UploadDir(dst string, src string, exclude []string) error
 func (c *communicator) Download(path string, w io.Writer) (err error) {
 	// Serve a single connection and a single copy
 	streamId := c.mux.NextId()
-	go serveSingleCopy("downloadWriter", c.mux, streamId, w, nil)
+
+	waitServer := make(chan bool)
+
+	go func() {
+		serveSingleCopy("downloadWriter", c.mux, streamId, w, nil)
+		waitServer <- true
+	}()
 
 	args := CommunicatorDownloadArgs{
 		Path:           path,
@@ -145,6 +152,9 @@ func (c *communicator) Download(path string, w io.Writer) (err error) {
 	}
 
 	err = c.client.Call("Communicator.Download", &args, new(interface{}))
+
+	<-waitServer
+
 	return
 }
 

From 48565440272157c20612026d0f6815a5b27ec6fd Mon Sep 17 00:00:00 2001
From: Chris Bednarski <banzaimonkey@gmail.com>
Date: Mon, 12 Oct 2015 18:42:17 -0700
Subject: [PATCH 2/2] Add a comment to indicate why we're waiting on the
 channel

---
 packer/rpc/communicator.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packer/rpc/communicator.go b/packer/rpc/communicator.go
index 525418ee2..48c6ea09f 100644
--- a/packer/rpc/communicator.go
+++ b/packer/rpc/communicator.go
@@ -140,7 +140,6 @@ func (c *communicator) Download(path string, w io.Writer) (err error) {
 	streamId := c.mux.NextId()
 
 	waitServer := make(chan bool)
-
 	go func() {
 		serveSingleCopy("downloadWriter", c.mux, streamId, w, nil)
 		waitServer <- true
@@ -151,8 +150,10 @@ func (c *communicator) Download(path string, w io.Writer) (err error) {
 		WriterStreamId: streamId,
 	}
 
+	// Start sending data to the RPC server
 	err = c.client.Call("Communicator.Download", &args, new(interface{}))
 
+	// Wait for the RPC server to finish receiving the data before we return
 	<-waitServer
 
 	return