I set the prospectors to ingest Nginx log to ES by fileBeat 5.5.0, and I found the type is "_type": "doc". I want to change the type name doc to other name, how to do it ?
**My config :**
filebeat.prospectors:
- type: log
  enabled: true
  paths:
    #- /var/log/*.log
    # 
    - D:\nginx-1.13.8\logs\access.log
    #- c:\programdata\elasticsearch\logs\*
    
**The  indexed document  in the ES.**
{
  "_index": "filebeat-2018.03.20",
  "_type": **"doc",**
  "_id": "P7-2Q2IBoQbqqlRr8Tx9",
  "_version": 1,
  "_score": 1,
  "_source": {
    "@timestamp": "2018-03-20T14:01:20.288Z",
    "beat": {
      "hostname": "HQ-PAB41656",
      "name": "HQ-PAB41656",
      "version": "5.5.0"
    },
    "input_type": "log",
    "message": "2018/03/20 22:01:11 [error] 7628#11008: *71 CreateFile() \"D:\\nginx-1.13.8/html/gggg\" failed (2: The system cannot find the file specified), client: 127.0.0.1, server: localhost, request: \"GET /gggg HTTP/1.1\", host: \"localhost:808\"",
    "offset": 35280,
    "source": "D:\\nginx-1.13.8\\logs\\error.log",
    "type": "log"
  },
  "fields": {
    "@timestamp": [
      "2018-03-20T14:01:20.288Z"
    ]
  }
}