How to make an HTTP request in golang with best practices?

Making a HTTP request in golang is pretty straightforward and simple, following are the examples by HTTP verbs

GET

The HTTP GET method requests a representation of the specified resource. Requests using GET should only retrieve data.

package main

import (
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
)
func main() {
  resp, err := http.Get("https://httpbin.org/get")
  if err != nil {
      log.Fatal(err)
  }
  defer resp.Body.Close()
  body, err := ioutil.ReadAll(resp.Body)
  if err != nil {
      log.Fatal(err)
  }
  fmt.Println(string(body))
}

GET with Query Args

package main

import (
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
)
func main() {
    client := &http.Client{}
    req, err := http.NewRequest(http.MethodGet, "https://httpbin.org/get", nil)
    if err != nil {
        log.Fatal(err)
    }
// appending to existing query args
q := req.URL.Query()
q.Add("foo", "bar")

// assign encoded query string to http request
req.URL.RawQuery = q.Encode()

resp, err := client.Do(req)
if err != nil {
    fmt.Println("Errored when sending request to the server")
    return
}

defer resp.Body.Close()
responseBody, err := ioutil.ReadAll(resp.Body)
if err != nil {
    log.Fatal(err)
}

fmt.Println(resp.Status)
fmt.Println(string(responseBody))

}

POST

The following example sends a POST request with data in JSON format.

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
)
func main() {
    values := map[string]string{"foo": "baz"}
    jsonData, err := json.Marshal(values)
req, err := http.NewRequest(http.MethodPost, "https://httpbin.org/post", bytes.NewBuffer(jsonData))
if err != nil {
    log.Fatal(err)
}

// appending to existing query args
q := req.URL.Query()
q.Add("foo", "bar")

// assign encoded query string to http request
req.URL.RawQuery = q.Encode()

client := &http.Client{}
resp, err := client.Do(req)
if err != nil {
    fmt.Println("Errored when sending request to the server")
    return
}

defer resp.Body.Close()
responseBody, err := ioutil.ReadAll(resp.Body)
if err != nil {
    log.Fatal(err)
}

fmt.Println(resp.Status)
fmt.Println(string(responseBody))

}

Best Practices

Re-use HTTP Client

The HTTP 1.1 protocol supports HTTP Persistent connections, or also known as HTTP Keep-Alive. This allows a client and a server to re-use the same underlying TCP connection when sending multiple HTTP Requests/Responses. So instead of establishing a connection for each HTTP Request, the client re-uses the TCP connection previously created more than once. This is particularly useful for performance reasons and when sending multiple requests to the same host.

func httpClient() *http.Client {
    client := &http.Client{Timeout: 10 * time.Second}
    return client
}

Reuse the http.Client throughout your code base.

An example of it as follows:

package main

import (
    "bytes"
    "io/ioutil"
    "log"
    "net/http"
    "time"
)
func httpClient() *http.Client {
    client := &http.Client{Timeout: 10 * time.Second}
    return client
}
func sendRequest(client *http.Client, method string) []byte {
    endpoint := "https://httpbin.org/post"
      values := map[string]string{"foo": "baz"}
    jsonData, err := json.Marshal(values)
req, err := http.NewRequest(method, endpoint, bytes.NewBuffer(jsonData))
if err != nil {
    log.Fatalf("Error Occurred. %+v", err)
}

response, err := client.Do(req)
if err != nil {
    log.Fatalf("Error sending request to API endpoint. %+v", err)
}

// Close the connection to reuse it
defer response.Body.Close()

body, err := ioutil.ReadAll(response.Body)
if err != nil {
    log.Fatalf("Couldn't parse response body. %+v", err)
}

return body

}
func main() {
  // c should be re-used for further calls
    c := httpClient()
    response := sendRequest(c, http.MethodPost)
    log.Println("Response Body:", string(response))
}