Update doc.go

Bump version to v0.5.2

client.go

@@ -996,7 +996,7 @@ func (c *Client) DialWithContext(dialCtx context.Context) error {
 // Returns:
 //   - An error if the disconnection fails; otherwise, returns nil.
 func (c *Client) Close() error {
-	if !c.smtpClient.HasConnection() {
+	if c.smtpClient == nil || !c.smtpClient.HasConnection() {
 		return nil
 	}
 	if err := c.smtpClient.Quit(); err != nil {

client_test.go

@@ -1647,6 +1647,15 @@ func TestClient_Close(t *testing.T) {
 			t.Errorf("close was supposed to fail, but didn't")
 		}
 	})
+	t.Run("close on a nil smtpclient should return nil", func(t *testing.T) {
+		client, err := NewClient(DefaultHost)
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+		if err = client.Close(); err != nil {
+			t.Errorf("failed to close the client: %s", err)
+		}
+	})
 }
 
 func TestClient_DialWithContext(t *testing.T) {

doc.go

@@ -11,4 +11,4 @@ package mail
 
 // VERSION indicates the current version of the package. It is also attached to the default user
 // agent string.
-const VERSION = "0.5.1"
+const VERSION = "0.5.2"