Making HTTP Requests in Go with Core Packages

  • Go
  • Gabriele Romanato

Go provides excellent support for working with HTTP requests through its net/http package. In this article, we'll see how to make GET and POST requests using only the packages included in Go's standard library.

Making a GET Request

To send a GET request, we can use the http.Get function. Here's an example:

package main

import (
    "fmt"
    "io"
    "net/http"
)

func main() {
    resp, err := http.Get("https://example.com")
    if (err != nil) {
        panic(err)
    }
    defer resp.Body.Close()

    body, err := io.ReadAll(resp.Body)
    if (err != nil) {
        panic(err)
    }

    fmt.Println(string(body))
}

In the code above:

  • We call http.Get with the desired URL.
  • We check for errors and remember to close the response body using defer.
  • We use io.ReadAll to read the entire response body.

Making a POST Request

To send data with a POST request, we can use http.Post or manually create a request with http.NewRequest. Here's a simple example using http.Post:

package main

import (
    "bytes"
    "fmt"
    "io"
    "net/http"
)

func main() {
    data := []byte(`{"name":"John","age":30}`)
    resp, err := http.Post("https://example.com/api", "application/json", bytes.NewBuffer(data))
    if (err != nil) {
        panic(err)
    }
    defer resp.Body.Close()

    body, err := io.ReadAll(resp.Body)
    if (err != nil) {
        panic(err)
    }

    fmt.Println(string(body))
}

Here:

  • We prepare the data to send as JSON.
  • We call http.Post specifying the URL, content type, and body.
  • We read and print the response as in the GET case.

Handling Custom Requests

For more control, we can manually create a request using http.NewRequest and send it with http.Client:

package main

import (
    "bytes"
    "fmt"
    "io"
    "net/http"
)

func main() {
    client := &http.Client{}

    req, err := http.NewRequest("PUT", "https://example.com/resource", bytes.NewBuffer([]byte(`{"update":"true"}`)))
    if (err != nil) {
        panic(err)
    }
    req.Header.Set("Content-Type", "application/json")

    resp, err := client.Do(req)
    if (err != nil) {
        panic(err)
    }
    defer resp.Body.Close()

    body, err := io.ReadAll(resp.Body)
    if (err != nil) {
        panic(err)
    }

    fmt.Println(string(body))
}

This approach allows you to:

  • Specify the HTTP method (such as PUT, PATCH, DELETE).
  • Add custom headers.
  • Use a custom http.Client.

Conclusion

With the net/http package and io functions, Go makes it simple to send HTTP requests in a robust and performant way, without needing external libraries.

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