slack.rb

require 'net/http'
require 'uri'
require 'json'

uri = URI.parse("https://hooks.slack.com/services/****")
payload = {
  text: "こんなかんじでいける",
  channel: "@dareka",
  username: "oreore",
  icon_emoji: ":ghost:"
}

Net::HTTP.post_form(uri, { payload: payload.to_json })

Good job!