Merge pull request #4701 from hashicorp/phinze/fix-race-winrm

communicator/winrm: fix data race in io copy

communicator/winrm/communicator.go

@@ -7,6 +7,7 @@ import (
 	"math/rand"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/hashicorp/terraform/communicator/remote"
@@ -148,10 +149,20 @@ func (c *Communicator) Start(rc *remote.Cmd) error {
 func runCommand(shell *winrm.Shell, cmd *winrm.Command, rc *remote.Cmd) {
 	defer shell.Close()
 
-	go io.Copy(rc.Stdout, cmd.Stdout)
-	go io.Copy(rc.Stderr, cmd.Stderr)
+	var wg sync.WaitGroup
+	go func() {
+		wg.Add(1)
+		io.Copy(rc.Stdout, cmd.Stdout)
+		wg.Done()
+	}()
+	go func() {
+		wg.Add(1)
+		io.Copy(rc.Stderr, cmd.Stderr)
+		wg.Done()
+	}()
 
 	cmd.Wait()
+	wg.Wait()
 	rc.SetExited(cmd.ExitCode())
 }