Strip newlines from Slack payload

Signed-off-by: Marcus Noble <github@marcusnoble.co.uk>

slack.go

@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/json"
 	"fmt"
+	"strings"
 
 	"github.com/gofiber/fiber/v2"
 	"github.com/slack-go/slack"
@@ -13,8 +14,11 @@ import (
 )
 
 func HandleSlackPayloadPost(c *fiber.Ctx) error {
+	body := string(c.Body())
+	body = strings.ReplaceAll(body, "\n", "\\n")
+
 	payload := slack.WebhookMessage{}
-	if err := c.BodyParser(&payload); err != nil {
+	if err := json.Unmarshal([]byte(body), &payload); err != nil {
 		fmt.Println("Failed to parse payload", string(c.Body()), err)
 		return err
 	}