VPC Tips for me?

Serverless Framework
6

I tried all solutions exposed here and in other topics but I still fail configuring a lambda to connect to an existing VPC: the lambda is always in “NO VPC”. I use sls 1.26.0. This is my serverless.yml file (I replace sensitive data by xxx):

service: myservice
provider:
  name: aws
  stage: ${opt:stage, 'dev'}
  region: eu-west-1
  environment:
    STAGE: ${self:provider.stage}

package:
  artifact: dist.zip

functions:
  metrics-to-splunk:
    handler: LogForwardingToSplunk.handler
    timeout: 300
    memorySize: 1024
    runtime: nodejs6.10
    vpc:
      securityGroupsIds:
        - sg-xxxxx
      subnetIds:
        - subnet-xxxx
        - subnet-xxxx
  environment:
      SPLUNK_HEC_URL: https://xxxxx
      SPLUNK_HEC_TOKEN: xxxxx

Could someone show me a working full example? Or point me to what I did wrong?