How to declare auto increment for id field in nodejs express in postgresql?

Question

PostgreSQL

How to declare auto increment for id field in nodejs express in postgresql?
Here is the code of my model created via strongloop

{
  "name": "Message",
  "base": "",
  "idInjection": true,
  "options": {
    "validateUpsert": true
  },
  "properties": {
    "content": {
      "type": "string",
      "required": true
    },
    "parent_id": {
      "type": "Message"
    },
    "created": {
      "type": "date"
    },
    "updated": {
      "type": "date"
    },
    "deleted": {
      "type": "boolean"
    },
    "id": {
      "type": "string",
      "id": true,
      "generated": true,
      "index": true
    },
    "receiver_id": {
      "type": "User",
      "required": true
    },
    "sender_id": {
      "type": "User",
      "required": true
    }
  },
  "validations": [],
  "relations": {},
  "acls": [],
  "methods": {}
}