Configure custom Prometheus Alertmanager templates in docker-compose

Question

Could you help me configure the Prometheus Alertmanager custom templates in docker-compose? I tried to write down the path to the templates, but seems I do something wrong.

There is a code of my docker-compose:

 alertmanager:
    image: prom/alertmanager
    container_name: alertmanager
    hostname: alertmanager
    restart: always
    ports:
      - "9093:9093"
    volumes:
      - ./alertmanager/alertmanager.yml:/etc/alertmanager/alertmanager.yml
      - ./alertmanager/templates/:/etc/alertmanager/templates/
    command:
      - '--config.file=/etc/alertmanager/alertmanager.yml'

This is alertmanager.yml

global:
  resolve_timeout: 1m

route:
  group_by: ['alertname']
  group_wait: 3s
  receiver: 'telegram_bot'

receivers:
- name: 'telegram_bot'
  telegram_configs:
  - bot_token: '12345678:AAAAAAAAAAAAAAAAAAAAAAAAAAA'
    api_url: 'https://api.telegram.org'
    chat_id: -1000000000000
    parse_mode: 'HTML'
templates:
- /etc/alertmanager/templates/telegram.tmpl

It won't work

How to properly integrate my own custom Alertmanager template into docker-compose?