Elasticsearch client for Go (Golang): complete guide to working with ES

Elasticsearch client for Go (Golang): a powerful tool for working with search

Elasticsearch is a distributed search and analytics system based on Apache Lucene that enables full-text search, aggregations, and real-time analytics. To interact with Elasticsearch from the Go (Golang) language, there is an official client — go-elasticsearch. This is a library developed and maintained by the Elastic team that provides a complete set of tools for working with the Elasticsearch REST API.

Features and advantages of go-elasticsearch

The go-elasticsearch library offers Go developers the following capabilities:

• Full support for the Elasticsearch API — all API versions, including indexing, search, aggregations, cluster management, and settings.
• Typed helper functions — simplify creating queries and processing responses.
• Support for bulk operations — mass insertion, updating, and deletion of documents.
• Automatic connection management — connection pool, retries on errors, and load balancing.
• Compatibility with Go modules — easy installation and updates via go get.
• Support for contexts — request cancellation and timeouts.
• Extensibility — the ability to create custom transports and middleware.

Installation and configuration

To install the library, run the command:

go get github.com/elastic/go-elasticsearch/v8

After installation, you can create a client with basic settings:

package main

import (    "log"    "github.com/elastic/go-elasticsearch/v8")

func main() {    cfg := elasticsearch.Config{        Addresses: []string{            "http://localhost:9200",        },    }    es, err := elasticsearch.NewClient(cfg)    if err != nil {        log.Fatalf("Error creating client: %s", err)    }    log.Println("Elasticsearch client successfully created")}

To connect to a cluster with authentication, specify the username and password:

cfg := elasticsearch.Config{    Addresses: []string{"https://your-cluster-url:9200"},    Username:  "elastic",    Password:  "your_password",}

Basic data operations

Creating an index

res, err := es.Indices.Create("my_index")if err != nil {    log.Fatalf("Error creating index: %s", err)}defer res.Body.Close()log.Println(res.String())

Indexing a document

To add a document, use the Index method:

package main

import (    "bytes"    "encoding/json"    "log"    "github.com/elastic/go-elasticsearch/v8")

type Book struct {    Title  string `json:"title"`    Author string `json:"author"`    Year   int    `json:"year"`}

func main() {    es, _ := elasticsearch.NewClient(elasticsearch.Config{        Addresses: []string{"http://localhost:9200"},    })

    book := Book{        Title:  "War and Peace",        Author: "Leo Tolstoy",        Year:   1869,    }

    data, _ := json.Marshal(book)    res, err := es.Index("books", bytes.NewReader(data))    if err != nil {        log.Fatalf("Error indexing: %s", err)    }    defer res.Body.Close()    log.Println(res.String())}

Searching documents

Search is performed using the Search method with a request body in JSON format:

query := `{    "query": {        "match": {            "author": "Tolstoy"        }    }}`

res, err := es.Search(    es.Search.WithIndex("books"),    es.Search.WithBody(bytes.NewReader([]byte(query))),    es.Search.WithPretty(),)if err