feat: add possibility to send msg to thread (#10)

Author: kseniyashaydurova

README.md

@@ -27,6 +27,7 @@ __NOTE__: The module supports up to 8 Fields in an [attachment](https://api.slac
 | fallback              | SLACK_FALLBACK      | A plain-text summary of the attachment. This text will be used in clients that don't show formatted text                             |
 | color                 | SLACK_COLOR         | An optional value that can either be one of `good`, `warning`, `danger`, or a color code (_e.g._ `#439FE0`)                          |
 | channel               | SLACK_CHANNEL       | Slack channel to send to                                                                                                             |
+| thread                | SLACK_THREAD        | Slack channel thread to send to                                                                                                      |
 | pretext               | SLACK_PRETEXT       | Optional text that appears above the message attachment block                                                                        |
 | author_name           | SLACK_AUTHOR_NAME   | Small text to display the attachment author's name                                                                                   |
 | author_link           | SLACK_AUTHOR_LINK   | URL that will hyperlink the author's name. Will only work if `author_name` is present                                                |

main.go

@@ -15,6 +15,7 @@ var (
 	fallback    = flag.String("fallback", os.Getenv("SLACK_FALLBACK"), "A plain-text summary of the attachment. This text will be used in clients that don't show formatted text")
 	color       = flag.String("color", os.Getenv("SLACK_COLOR"), "An optional value that can either be one of good, warning, danger, or any hex color code (e.g. #439FE0)")
 	channel     = flag.String("channel", os.Getenv("SLACK_CHANNEL"), "Slack channel to send to")
+	thread      = flag.String("thread", os.Getenv("SLACK_THREAD"), "Slack channel thread to send to")
 	pretext     = flag.String("pretext", os.Getenv("SLACK_PRETEXT"), "Optional text that appears above the message attachment block")
 	authorName  = flag.String("author_name", os.Getenv("SLACK_AUTHOR_NAME"), "Small text to display the attachment author's name")
 	authorLink  = flag.String("author_link", os.Getenv("SLACK_AUTHOR_LINK"), "URL that will hyperlink the author's name. Will only work if author_name is present")
@@ -135,6 +136,7 @@ func main() {
 		Username:    *userName,
 		IconEmoji:   *iconEmoji,
 		Channel:     *channel,
+		Thread:      *thread,
 	}
 
 	notifier := NewSlackNotifier(*webhookURL)

slack_notifier.go

@@ -22,6 +22,7 @@ type Payload struct {
 	IconEmoji   string       `json:"icon_emoji"`
 	Username    string       `json:"username"`
 	Channel     string       `json:"channel"`
+	Thread      string       `json:"thread_ts,omitempty"`
 }
 
 // Attachment for a Slack message