golang: client declared and not used

I'm doing tests with the go library for elasticsearch: link

I have the following code that is my library to connect to the Elasticsearch server:

package elasticsearch

import (
    "fmt"
    "os"
    elastic "gopkg.in/olivere/elastic.v5"
    "context"
)

var client *elastic.Client

func init() {

    var err error

    client, err := elastic.NewClient(
        elastic.SetURL(os.Getenv("ELASTICSEARCH_ENTRYPOINT")),
        elastic.SetBasicAuth(os.Getenv("ELASTICSEARCH_USERNAME"), os.Getenv("ELASTICSEARCH_PASSWORD")),
    )
    if err != nil {
        panic(err)
    }

}

func Ping() (string, error) {

    ctx := context.Background()
    info, code, err := client.Ping(os.Getenv("ELASTICSEARCH_ENTRYPOINT")).Do(ctx)
    if err != nil {
        panic(err)
    }
    msg := fmt.Sprintf("Elasticsearch returned with code %d and version %s", code, info.Version.Number)
    return msg, nil

}

And my main program is as follows:

package main

import (
    "fmt"
    _ "github.com/hectorgool/gomicrosearch3/elasticsearch"
)

func main() {

    if result, err := elasticsearch.Ping(); err != nil {
        fmt.Printf("Error: %s\n", err)
    } else {
        fmt.Printf("ElasticSearch result: '%s'\n", result)
    }

}

But when you run the program with:

go run main.go

It shows me the following:

elasticsearch / elasticsearch.go: 18: client declared and not used

Line 18 corresponds to the following block of code:

client, err := elastic.NewClient(
    elastic.SetURL(os.Getenv("ELASTICSEARCH_ENTRYPOINT")),
    elastic.SetBasicAuth(os.Getenv("ELASTICSEARCH_USERNAME"), os.Getenv("ELASTICSEARCH_PASSWORD")),
)

Someone can tell me what the program is missing or what I am doing wrong.