What is the proper way to introduce headers with TOKEN in a asynco aiohttp API request?

I need to download many different users data in a very slow API, so I decided to make parallel requests. After trying multithreads and multiprocess I decided asynco download would be the best in my case, and my code works for some cases I have tried without the header that includes the Bearer Auth... But in this case it gives ClientConnectorCertificateError... Any ideas what I am doing wrong?

import aiohttp
import asyncio
import time

start_time = time.time()
headers =  {'accept': 'application/json','Authorization': "Bearer {}".format(token)}

async def get_cch(session, url):
    async with session.get(url, headers=headers) as resp:
        cch = await resp.json()
        x= cch['data']['contractId']
        return open(f'{x}.json', 'w').write(json.dumps(cch))


async def main():

    async with aiohttp.ClientSession(headers=headers) as session:

        tasks = []
        for contract in range(len(file_name_list)):
            start_date = '2018-01-01'
            end_date = '2018-01-05'
            url = 'https://apinergia.somenergia.coop/cch/'+file_name_list[contract]+'?tariff=None&type=tg_cchfact&from_='+start_date+'&to_='+end_date+'&limit=30000'
            tasks.append(asyncio.ensure_future(get_cch(session, url)))

        original_cch = await asyncio.gather(*tasks)
        for cch in original_cch:
            print(cch)

await main()

print("--- %s seconds ---" % (time.time() - start_time))