Logstash ssl error es input --> output csv

I'm getting the following error when running a logstash:

tric=>true, charset=>"UTF-8">, size=>1000, scroll=>"1m", docinfo=>false, docinfo_target=>"@metadata", docinfo_fields=>["_index", "_type", "_id"], ssl=>false>
Error: certificate verify failed
Exception: Faraday::SSLError
Stack: org/jruby/ext/openssl/SSLSocket.java:276:in connect_nonblock' uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/net/protocol.rb:44:inssl_socket_connect'
uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/net/http.rb:985:in `connect'

Config file

input {
elasticsearch {
hosts => ["https://monk.es.net:9200"]
ca_file => '/etc/logstash/config/certs/ca.crt'
user => elastic
password => oCAB6B
index => "daily_link-*"
query => '
{
"query": {
"multi_match": {
"query" : "2019-08-01"
}
}
}
'
}
}
output {
csv {
# elastic field name
fields => ["date", "instance", "transmitted", "received","octets transmitted","octets received","received requiring ok"]
path => "/tmp/csv-export.csv"
}
}