Example of the Telegram Bot

Based on https://iamondemand.com/blog/building-your-first-serverless-telegram-bot/ and https://gitlab.com/Athamaxy/telegram-bot-tutorial/-/blob/main/TutorialBot.go

Should cost nothing due to Google Cloud Provider Free plan.

Setup

Build and download dependencies

Run go get -t . from the root. Next go mod tidy.

Register new bot in Telegram

https://telegram.me/BotFather

It will provide TELEGRAM_APITOKEN and link to a bot in Telegram.

Provide bot with TELEGRAM_APITOKEN and try locally

Create ".env" file in the root and set content as

TELEGRAM_APITOKEN=<token_received_in_step_before_without_triangle_brackets>
TELEGRAM_DEBUG=true

Try bot in "poll Telegram" mode with go run bot-local-polling.go from repo root. After 'Start listening for updates. Press Enter key to stop' bot in Telegram application should start to work - try to write phrases or '/help' to it. To stop press Enter.

To check that function works in "listen requests" mode (i.e. without connecting to Telegram as in previous case but waiting Telegram to initiate connection) run go run telegrambot/cmd/bot-local-listen.go. After 'Serving function: "HandleTelegramWebHook"' message try to check it with curl -X POST http://localhost:8080/ -d '{"some": true}' - app should print something like "Received unsupported update: {0 }".

Load to GCP Function

• Install gcloud CLI. It should support "Generation v2" functions (--gen2 argument in command gcloud functions deploy which is listed below).
• Login in gcloud with gcloud auth login command.
• Create new project with gcloud projects create {PROJECT_NAME}. Note that there are a lot of limitations to project name.
• Switch gcloud to use this project with gcloud config set project {PROJECT_NAME}.
• Get project unique number with gcloud projects describe {PROJECT_NAME} - it would be in "projectNumber" field. BTW only after this command gcloud projects list will start to show your new project. New project may be checked somewhere on https://console.cloud.google.com/home.
• TODO Create a vendor directory using the contents of go.mod file with go mod vendor. It will created "vendor" directory with dependencies.
• Get your Go version with go version. Find closest or more suitable on https://cloud.google.com/functions/docs/concepts/go-runtime#gcloud to use as an argument to the next command.
• Create secret to store Telegram Bot API with gcloud secrets create telegram-bot-secret --replication-policy="automatic" (type "y" when/if it asks for enabling API). Upload secret with gcloud secrets versions add telegram-bot-secret --data-file=".env". It may be checked on https://console.cloud.google.com/security/secret-manager/secret/telegram-bot-secret/.
• Allow GCP Function access to new secret with gcloud secrets add-iam-policy-binding telegram-bot-secret --member='projects/alexanderm-telegram-bot/secrets/telegram-bot-secret/versions/latest' --role='roles/secretmanager.secretAccessor'. TODO

"2022/11/21 20:17:23 Can't read 'telegram-bot-secret' secret: Failed to access secret version: rpc error: code = PermissionDenied desc = Permission 'secretmanager.versions.access' denied for resource 'projects/alexanderm-telegram-bot/secrets/telegram-bot-secret/versions/latest' (or it may not exist)."

• Run

  gcloud functions deploy telegram-bot \
  --gen2 \
  --runtime=go116 \
  --region={REGION} \
  --source=. \
  --entry-point=HandleTelegramWebHook \
  --trigger-http \
  --allow-unauthenticated \
  --set-env-vars=GCP_PROJECT_NAME={PROJECT_NAME}

  • It will ask you "API [cloudfunctions.googleapis.com/artifactregistry.googleapis.com/run.googleapis.com press] not enabled " - just press'y' for all and wait.
  • If it failed with "...failed as the billing account is not available" then need to open https://console.cloud.google.com/home/dashboard?project={PROJECT_NAME} and enable billing in it - https://cloud.google.com/billing/docs/how-to/modify-project (it will ask you for billing data to charge in case of breaking free limits).
  • If it failed with "Cloud Build API has not been used in project ... before or it is disabled. Enable it by visiting ..." then need to enable it and/or wait few minutes until it start work.
  • If it failed with "... Permission 'storage.objects.get' denied on resource ..." then it is probably because of issue above and you need to wait more.

Inform Telegram to don't wait bot connection but reach it by WEB hook instead

Execute curl --request POST --url https://api.telegram.org/bot<TELEGRAM_TOKEN>/setWebhook --header 'content-type: application/json' --data '{"url": "<LINK_YOU_GET_FROM_SERVERLESS_DEPLOY>"}'