From 2516d1055a7a24e17ba953a5e8791690a51c29c8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20B=C3=B6gle?= <Jonas@sandstorm-projects.de>
Date: Fri, 8 Feb 2019 20:36:50 +0100
Subject: [PATCH 1/2] fix concurrency

---
 client.go      | 12 +++++++++++-
 client_test.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/client.go b/client.go
index 0028ddc..e555a6d 100644
--- a/client.go
+++ b/client.go
@@ -7,6 +7,7 @@ import (
 	"net"
 	"regexp"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -57,6 +58,7 @@ type Client struct {
 	notify        chan Notification
 	disconnect    chan struct{}
 	res           []string
+	mutex         sync.Mutex
 
 	Server *ServerMethods
 }
@@ -234,7 +236,15 @@ func (c *Client) ExecCmd(cmd *Cmd) ([]string, error) {
 		return nil, ErrNotConnected
 	}
 
-	c.work <- cmd.String()
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	select {
+	case c.work <- cmd.String():
+		// continue
+	case <-time.After(c.timeout):
+		return nil, ErrTimeout
+	}
 
 	select {
 	case err := <-c.err:
diff --git a/client_test.go b/client_test.go
index cdc028d..e50c438 100644
--- a/client_test.go
+++ b/client_test.go
@@ -230,3 +230,36 @@ func TestClientBadHeader(t *testing.T) {
 	// Should never get here
 	assert.NoError(t, c.Close())
 }
+
+func TestConcurrency(t *testing.T) {
+	s := newServer(t)
+	if s == nil {
+		return
+	}
+	defer func() {
+		assert.NoError(t, s.Close())
+	}()
+
+	c, err := NewClient(s.Addr, Timeout(time.Millisecond*100))
+	if !assert.NoError(t, err) {
+		return
+	}
+
+	wait := make(chan struct{})
+
+	go func() {
+		for i := 0; i <= 10; i++ {
+			_, err = c.Server.GroupList()
+			assert.NoError(t, err)
+		}
+		wait <- struct{}{}
+	}()
+
+	for i := 0; i <= 10; i++ {
+		_, err = c.Server.GroupList()
+		assert.NoError(t, err)
+	}
+
+	// wait for go routine to finish
+	<-wait
+}

From 94d0c84d7ba3ffa6a4306867e9708bf372c47e71 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20B=C3=B6gle?= <Jonas@sandstorm-projects.de>
Date: Sun, 10 Feb 2019 15:38:56 +0100
Subject: [PATCH 2/2] fixed TestConcurrency

---
 client_test.go | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/client_test.go b/client_test.go
index e50c438..a02d826 100644
--- a/client_test.go
+++ b/client_test.go
@@ -245,21 +245,26 @@ func TestConcurrency(t *testing.T) {
 		return
 	}
 
-	wait := make(chan struct{})
+	const iterations = 10
+	errors := make(chan error)
 
 	go func() {
-		for i := 0; i <= 10; i++ {
-			_, err = c.Server.GroupList()
-			assert.NoError(t, err)
+		defer close(errors)
+
+		for i := 0; i <= iterations; i++ {
+			if _, err2 := c.Server.GroupList(); err2 != nil {
+				errors <- err2
+			}
 		}
-		wait <- struct{}{}
 	}()
 
-	for i := 0; i <= 10; i++ {
+	for i := 0; i <= iterations; i++ {
 		_, err = c.Server.GroupList()
 		assert.NoError(t, err)
 	}
 
-	// wait for go routine to finish
-	<-wait
+	// receive errors from go-routine and wait for completion
+	for err := range errors {
+		assert.NoError(t, err)
+	}
 }