error[39m: (SEARCH/ELASTICSEARCH) Index Check Error: self signed certificate in certificate chain

[heavenkiller2018]

Question
Describe in details what you are trying to achieve and where do you need guidance.
when I use elasticsearch for Search Engine, the following mistake occured that I found in logs:

2020-04-02T02:38:54.557Z [MASTER] �[32minfo�[39m: (SEARCH/ELASTICSEARCH) Initialization completed.
2020-04-02T02:39:05.082Z [MASTER] �[33mwarn�[39m: Search Engine Error: self signed certificate in certificate chain
2020-04-02T02:39:06.658Z [MASTER] �[33mwarn�[39m: Search Engine Error: self signed certificate in certificate chain
2020-04-02T02:40:25.934Z [MASTER] �[32minfo�[39m: (SEARCH/ELASTICSEARCH) Initializing...
2020-04-02T02:40:25.963Z [MASTER] �[31merror�[39m: (SEARCH/ELASTICSEARCH) Index Check Error: self signed certificate in certificate chain
2020-04-02T02:40:25.963Z [MASTER] �[32minfo�[39m: (SEARCH/ELASTICSEARCH) Initialization completed.
2020-04-02T02:40:42.179Z [MASTER] �[33mwarn�[39m: Search Engine Error: self signed certificate in certificate chain
2020-04-02T02:47:00.693Z [MASTER] �[33mwarn�[39m: Search Engine Error: self signed certificate in certificate chain

what happened? I use ssl encrypted elasticsearch as backend and of course self signed certificate becauseof in intranet network.

how to ingore this situation 'self signed certificate in certificate chain'?
just like the same thing done in curl:
when I use curl without '-k' :
curl https://username:pass@elasticsearch-master:9200
the secure tip like this:

More details here: http://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
 the bundle, the certificate verification probably failed due to a
 problem with the certificate (it might be expired, or the name might
 not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
 the -k (or --insecure) option.

then I type the same command with 'K', all is right.
curl https://username:pass@elasticsearch-master:9200 -k

{
  "name" : "elasticsearch-master-1",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "dbMdnhigRjOoSsMnb6L-dw",
  "version" : {
    "number" : "7.6.1",
    "build_flavor" : "default",
    "build_type" : "docker",
    "build_hash" : "aa751e09be0a5072e8570670309b1f12348f023b",
    "build_date" : "2020-02-29T00:15:25.529771Z",
    "build_snapshot" : false,
    "lucene_version" : "8.4.0",
    "minimum_wire_compatibility_version" : "6.8.0",
    "minimum_index_compatibility_version" : "6.0.0-beta1"
  },
  "tagline" : "You Know, for Search"
}

Host Info (please complete the following information):
OS: [e.g. Ubuntu 18.04, Docker] kubenetes 1.14.8
Wiki.js version: [e.g. 2.0.1] 2.1.113
Database engine: [e.g. postgres 9.7, mysql 5.7]