If you want your .env.{stage} deployed to lambda

If you do not specify your environment variables in the serverless.yaml file, they will not be deployed to your Lambda function. I haven’t known it because it worked on local without any problems..

service: user-consent
frameworkVersion: '3'

useDotenv: true

provider:
  name: aws
  region: ap-southeast-1
  environment:
    VARIABLE: ${env:VARIABLE}

  ...

If you don’t want this injection codes, just use serverless-dotenv-plugin, I don’t recommend it.