from telethon import functions, types
from telethon.sync import TelegramClient

with TelegramClient("name", api_id, api_hash) as client:
    result = client(functions.channels.GetParticipantsRequest(
        channel=channel_username,
        filter=types.ChannelParticipantsRecent(),
        offset=1,
        limit=200,
        hash=0
    ))
    users = [i for i in result.users]

def get_users_from_channel(client, channel_username):
    offset = 0
    limit = 100
    all_participants = []

    while True:
        participants = client(GetParticipantsRequest(
            channel_username, ChannelParticipantsSearch(''), offset, limit,
            hash=0
        ))
        if not participants.users:
            break
        all_participants.extend(participants.users)
        offset += len(participants.users)

    return all_participants