Post text notifications to a Slack channel using a webhook https://api.slack.com/incoming-webhooks

slack.rb

# frozen_string_literal: true

# 1. Manage your Slack apps at https://your_slack_team_name.slack.com/apps/manage
# 2. Create an 'Incoming WebHooks' configuration

require 'net/http'
require 'json'

class Slack
  def self.post(text, channel = '#channel', username = 'default username')
    # 3. Copy/paste the webhook here
    uri = URI('https://hooks.slack.com/services/your_webhook')
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    req = Net::HTTP::Post.new(uri.path, 'Content-Type' => 'application/json')
    req.body = { channel: channel, username: username, text: text }.to_json
    res = http.request(req)
  rescue StandardError => e
    puts "failed #{e}"
  end
end

test.rb

Slack.post("Some notification text")
Slack.post("Some notification text", "#notifications", "Github")