title: How to add cooldown mapping to users who reacted first?
body: <p>Im currently working on a cart manager where users has a chance of a giveaway prize (First come first serve). Basically I will automatically post some embeds and the person who reacts first will get the prize and a message written in DM's from the bot. The user who got the prize first will get a cooldown for 5 minutes (the reason of this is that the same user should not be able to get a second prize within 5 minutes)</p>
  <p>I have written something like this:</p>
  <pre><code># -*- coding: utf-8 -*-
  import asyncio
  from datetime import datetime
  
  from discord import Client, Embed, Object
  
  client = Client()
  
  lock = asyncio.Lock()
  
  PRIVATE_CHANNEL_ID = xxxxxxxxxxxxxx
  PUBLIC_CHANNEL_ID = xxxxxxxxxxxxx
  EMOJI_ID = &quot;\N{SHOPPING TROLLEY}&quot;
  
  # ----------------------------------------------------- #
  
  @client.event
  async def on_ready():
      print(f'{client.user.name} Logged In!')
  
  @client.event
  async def on_raw_reaction_add(payload):
      if payload.channel_id == PUBLIC_CHANNEL_ID and '\U0001f6d2' == str(payload.emoji) and payload.user_id != client.user.id:
          async with lock:
              # Check if person is rate limited
  </code></pre>
  <p>I have read abit regarding cooldown mapping and found an example of:</p>
  <pre><code>class SomeCog(commands.Cog):
      def __init__(self):
          self._cd = commands.CooldownMapping.from_cooldown(1.0, 60.0, commands.BucketType.user)
  
      async def cog_check(self, ctx):
          bucket = self._cd.get_bucket(ctx.message)
          retry_after = bucket.update_rate_limit()
          if retry_after:
              # you're rate limited
              # helpful message here
              pass
          # you're not rate limited
  </code></pre>
  <p>however my problem is that I do not know how to apply cooldown for a user who reacted first on given reaction and I wonder how can I do that? How can I apply a cooldown to the user to not be ablet o react for next 5 minutes using the <code>CooldownMapping</code>?</p>