functions:
  someFunction:
    events:
      - http:
          ....
          response:
            contentHandling: CONVERT_TO_BINARY

# serverless.yml
plugins:
  - serverless-apigwy-binary

# serverless.yml
functions:
  hello:
    handler: handler.hello
    events:
      - http:
          integration: lambda
          path: hello
          method: get
          contentHandling: CONVERT_TO_BINARY