Add CloseIdleConnections method to close tcp connections (#92)

client.go

@@ -45,6 +45,10 @@ type Client struct {
 	Host        string
 }
 
+type connectionCloser interface {
+	CloseIdleConnections()
+}
+
 // NewClient returns a new Client with an underlying http.Client configured with
 // the correct APNs HTTP/2 transport settings. It does not connect to the APNs
 // until the first Notification is sent via the Push method.
@@ -142,6 +146,13 @@ func (c *Client) PushWithContext(ctx Context, n *Notification) (*Response, error
 	return response, nil
 }
 
+// CloseIdleConnections closes any underlying connections which were previously
+// connected from previous requests but are now sitting idle. It will not
+// interrupt any connections currently in use.
+func (c *Client) CloseIdleConnections() {
+	c.HTTPClient.Transport.(connectionCloser).CloseIdleConnections()
+}
+
 func setHeaders(r *http.Request, n *Notification) {
 	r.Header.Set("Content-Type", "application/json; charset=utf-8")
 	if n.Topic != "" {

client_test.go

@@ -35,6 +35,15 @@ func mockClient(url string) *apns.Client {
 	return &apns.Client{Host: url, HTTPClient: http.DefaultClient}
 }
 
+type mockTransport struct {
+	*http2.Transport
+	closed bool
+}
+
+func (c *mockTransport) CloseIdleConnections() {
+	c.closed = true
+}
+
 // Unit Tests
 
 func TestClientDefaultHost(t *testing.T) {
@@ -231,3 +240,14 @@ func TestMalformedJSONResponse(t *testing.T) {
 	assert.Error(t, err)
 	assert.Equal(t, false, res.Sent())
 }
+
+func TestCloseIdleConnections(t *testing.T) {
+	transport := &mockTransport{}
+
+	client := mockClient("")
+	client.HTTPClient.Transport = transport
+
+	assert.Equal(t, false, transport.closed)
+	client.CloseIdleConnections()
+	assert.Equal(t, true, transport.closed)
+}