req

Simple Go HTTP client with Black Magic

Documentation

Full documentation is available on the official website: https://req.cool.

Features

Simple and Powerful: Simple and easy to use, providing rich client-level and request-level settings, all of which are intuitive and chainable methods.
Easy Debugging: Powerful and convenient debug utilities, including debug logs, performance traces, and even dump the complete request and response content (see Debugging).
Easy API Testing: API testing can be done with minimal code, no need to explicitly create any Request or Client, or even to handle errors (See Quick HTTP Test)
Smart by Default: Detect and decode to utf-8 automatically if possible to avoid garbled characters (See Auto Decode), marshal request body and unmarshal response body automatically according to the Content-Type.
Support Multiple HTTP Versions: Support HTTP/1.1, HTTP/2, and HTTP/3, and can automatically detect the server side and select the optimal HTTP version for requests, you can also force the protocol if you want (See Force HTTP version).
Support Retry: Support automatic request retry and is fully customizable (See Retry).
HTTP Fingerprinting: Support http fingerprint impersonation, so that we can access websites that prohibit crawler programs by identifying http fingerprints (See HTTP Fingerprint).
Multiple Authentication Methods: You can use HTTP Basic Auth, Bearer Auth Token and Digest Auth out of box (see Authentication).
Easy Download and Upload: You can download and upload files with simple request settings, and even set a callback to show real-time progress (See Download and Upload).
Exportable: req.Transport is exportable. Compared with http.Transport, it also supports HTTP3, dump content, middleware, etc. It can directly replace the Transport of http.Client in existing projects, and obtain more powerful functions with minimal code change.
Extensible: Support Middleware for Request, Response, Client and Transport (See Request and Response Middleware) and Client and Transport Middleware).

Get Started

Install

You first need Go installed (version 1.24+ is required), then you can use the below Go command to install req:

go get github.com/imroc/req/v3

Import

Import req to your code:

import "github.com/imroc/req/v3"

Basic Usage

# assume the following codes in main.go file
$ cat main.go

package main

import (
    "github.com/imroc/req/v3"
)

func main() {
    req.DevMode() // Treat the package name as a Client, enable development mode
    req.MustGet("https://httpbin.org/uuid") // Treat the package name as a Request, send GET request.

    req.EnableForceHTTP1() // Force using HTTP/1.1
    req.MustGet("https://httpbin.org/uuid")
}

$ go run main.go
2022/05/19 10:05:07.920113 DEBUG [req] HTTP/2 GET https://httpbin.org/uuid
:authority: httpbin.org
:method: GET
:path: /uuid
:scheme: https
user-agent: req/v3 (https://github.com/imroc/req/v3)
accept-encoding: gzip

:status: 200
date: Thu, 19 May 2022 02:05:08 GMT
content-type: application/json
content-length: 53
server: gunicorn/19.9.0
access-control-allow-origin: *
access-control-allow-credentials: true

{
  "uuid": "bd519208-35d1-4483-ad9f-e1555ae108ba"
}

2022/05/19 10:05:09.340974 DEBUG [req] HTTP/1.1 GET https://httpbin.org/uuid
GET /uuid HTTP/1.1
Host: httpbin.org
User-Agent: req/v3 (https://github.com/imroc/req/v3)
Accept-Encoding: gzip

HTTP/1.1 200 OK
Date: Thu, 19 May 2022 02:05:09 GMT
Content-Type: application/json
Content-Length: 53
Connection: keep-alive
Server: gunicorn/19.9.0
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true

{
  "uuid": "49b7f916-c6f3-49d4-a6d4-22ae93b71969"
}

The sample code above is good for quick testing purposes, which use DevMode() to see request details, and send requests using global wrapper methods that use the default client behind the scenes to initiate the request.

In production, it is recommended to explicitly create a client, and then use the same client to send all requests, please see other examples below.

Videos

The following is a series of video tutorials for req:

Youtube Play List
BiliBili 播放列表 (Chinese)

More

Check more introduction, tutorials, examples, best practices and API references on the official website.

Simple GET

package main

import (
    "fmt"
    "github.com/imroc/req/v3"
    "log"
)

func main() {
    client := req.C() // Use C() to create a client.
    resp, err := client.R(). // Use R() to create a request.
        Get("https://httpbin.org/uuid")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(resp)
}

{
  "uuid": "a4d4430d-0e5f-412f-88f5-722d84bc2a62"
}

Advanced GET

package main

import (
  "fmt"
  "github.com/imroc/req/v3"
  "log"
  "time"
)

type ErrorMessage struct {
  Message string `json:"message"`
}

type UserInfo struct {
  Name string `json:"name"`
  Blog string `json:"blog"`
}

func main() {
  client := req.C().
    SetUserAgent("my-custom-client"). // Chainable client settings.
    SetTimeout(5 * time.Second)

  var userInfo UserInfo
  var errMsg ErrorMessage
  resp, err := client.R().
    SetHeader("Accept", "application/vnd.github.v3+json"). // Chainable request settings.
    SetPathParam("username", "imroc"). // Replace path variable in url.
    SetSuccessResult(&userInfo). // Unmarshal response body into userInfo automatically if status code is between 200 and 299.
    SetErrorResult(&errMsg). // Unmarshal response body into errMsg automatically if status code >= 400.
    EnableDump(). // Enable dump at request level, only print dump content if there is an error or some unknown situation occurs to help troubleshoot.
    Get("https://api.github.com/users/{username}")

  if err != nil { // Error handling.
    log.Println("error:", err)
    log.Println("raw content:")
    log.Println(resp.Dump()) // Record raw content when error occurs.
    return
  }

  if resp.IsErrorState() { // Status code >= 400.
    fmt.Println(errMsg.Message) // Record error message returned.
    return
  }

  if resp.IsSuccessState() { // Status code is between 200 and 299.
    fmt.Printf("%s (%s)\n", userInfo.Name, userInfo.Blog)
    return
  }

  // Unknown status code.
  log.Println("unknown status", resp.Status)
  log.Println("raw content:")
  log.Println(resp.Dump()) // Record raw content when server returned unknown status code.
}

Normally it will output (SuccessState):

roc (https://imroc.cc)

More Advanced GET

You can set up a unified logic for error handling on the client, so that each time you send a request you only need to focus on the success situation, reducing duplicate code.

package main

import (
    "fmt"
    "github.com/imroc/req/v3"
    "log"
    "time"
)

type ErrorMessage struct {
    Message string `json:"message"`
}

func (msg *ErrorMessage) Error() string {
    return fmt.Sprintf("API Error: %s", msg.Message)
}

type UserInfo struct {
    Name string `json:"name"`
    Blog string `json:"blog"`
}

var client = req.C().
    SetUserAgent("my-custom-client"). // Chainable client settings.
    SetTimeout(5 * time.Second).
    EnableDumpEachRequest().
    SetCommonErrorResult(&ErrorMessage{}).
    OnAfterResponse(func(client *req.Client, resp *req.Response) error {
        if resp.Err != nil { // There is an underlying error, e.g. network error or unmarshal error.
            return nil
        }
        if errMsg, ok := resp.ErrorResult().(*ErrorMessage); ok {
            resp.Err = errMsg // Convert api error into go error
            return nil
        }
        if !resp.IsSuccessState() {
            // Neither a success response nor a error response, record details to help troubleshooting
            resp.Err = fmt.Errorf("bad status: %s\nraw content:\n%s", resp.Status, resp.Dump())
        }
        return nil
    })

func main() {
    var userInfo UserInfo
    resp, err := client.R().
        SetHeader("Accept", "application/vnd.github.v3+json"). // Chainable request settings
        SetPathParam("username", "imroc").
        SetSuccessResult(&userInfo). // Unmarshal response body into userInfo automatically if status code is between 200 and 299.
        Get("https://api.github.com/users/{username}")

    if err != nil { // Error handling.
        log.Println("error:", err)
        return
    }

    if resp.IsSuccessState() { // Status code is between 200 and 299.
        fmt.Printf("%s (%s)\n", userInfo.Name, userInfo.Blog)
    }
}

Simple POST

package main

import (
  "fmt"
  "github.com/imroc/req/v3"
  "log"
)

type Repo struct {
  Name string `json:"name"`
  Url  string `json:"url"`
}

type Result struct {
  Data string `json:"data"`
}

func main() {
  client := req.C().DevMode()
  var result Result

  resp, err := client.R().
    SetBody(&Repo{Name: "req", Url: "https://github.com/imroc/req"}).
    SetSuccessResult(&result).
    Post("https://httpbin.org/post")
  if err != nil {
    log.Fatal(err)
  }

  if !resp.IsSuccessState() {
    fmt.Println("bad response status:", resp.Status)
    return
  }
  fmt.Println("++++++++++++++++++++++++++++++++++++++++++++++++")
  fmt.Println("data:", result.Data)
  fmt.Println("++++++++++++++++++++++++++++++++++++++++++++++++")
}

2022/05/19 20:11:00.151171 DEBUG [req] HTTP/2 POST https://httpbin.org/post
:authority: httpbin.org
:method: POST
:path: /post
:scheme: https
user-agent: req/v3 (https://github.com/imroc/req/v3)
content-type: application/json; charset=utf-8
content-length: 55
accept-encoding: gzip

{"name":"req","website":"https://github.com/imroc/req"}

:status: 200
date: Thu, 19 May 2022 12:11:00 GMT
content-type: application/json
content-length: 651
server: gunicorn/19.9.0
access-control-allow-origin: *
access-control-allow-credentials: true

{
  "args": {},
  "data": "{\"name\":\"req\",\"website\":\"https://github.com/imroc/req\"}",
  "files": {},
  "form": {},
  "headers": {
    "Accept-Encoding": "gzip",
    "Content-Length": "55",
    "Content-Type": "application/json; charset=utf-8",
    "Host": "httpbin.org",
    "User-Agent": "req/v3 (https://github.com/imroc/req/v3)",
    "X-Amzn-Trace-Id": "Root=1-628633d4-7559d633152b4307288ead2e"
  },
  "json": {
    "name": "req",
    "website": "https://github.com/imroc/req"
  },
  "origin": "103.7.29.30",
  "url": "https://httpbin.org/post"
}

++++++++++++++++++++++++++++++++++++++++++++++++
data: {"name":"req","url":"https://github.com/imroc/req"}
++++++++++++++++++++++++++++++++++++++++++++++++

Do API Style

If you like, you can also use a Do API style like the following to make requests:

package main

import (
    "fmt"
    "github.com/imroc/req/v3"
)

type APIResponse struct {
    Origin string `json:"origin"`
    Url    string `json:"url"`
}

func main() {
    var resp APIResponse
    c := req.C().SetBaseURL("https://httpbin.org/post")
    err := c.Post().
        SetBody("hello").
        Do().
        Into(&resp)
    if err != nil {
        panic(err)
    }
    fmt.Println("My IP is", resp.Origin)
}

My IP is 182.138.155.113

The order of chain calls is more intuitive: first call Client to create a request with a specified Method, then use chain calls to set the request, then use Do() to fire the request, return Response, and finally call Response.Into to unmarshal response body into specified object.
Response.Into will return an error if an error occurs during sending the request or during unmarshalling.
The url of some APIs is fixed, and different types of requests are implemented by passing different bodies. In this scenario, Client.SetBaseURL can be used to set a unified url, and there is no need to set the url for each request when initiating a request. Of course, you can also call Request.SetURL to set it if you need it.

Build SDK With Req

Here is an example of building GitHub’s SDK with req, using two styles (GetUserProfile_Style1, GetUserProfile_Style2).

import (
    "context"
    "fmt"
    "github.com/imroc/req/v3"
)

type ErrorMessage struct {
    Message string `json:"message"`
}

// Error implements go error interface.
func (msg *ErrorMessage) Error() string {
    return fmt.Sprintf("API Error: %s", msg.Message)
}

type GithubClient struct {
    *req.Client
}

func NewGithubClient() *GithubClient {
    return &GithubClient{
        Client: req.C().
            SetBaseURL("https://api.github.com").
            SetCommonErrorResult(&ErrorMessage{}).
            EnableDumpEachRequest().
            OnAfterResponse(func(client *req.Client, resp *req.Response) error {
                if resp.Err != nil { // There is an underlying error, e.g. network error or unmarshal error.
                    return nil
                }
                if errMsg, ok := resp.ErrorResult().(*ErrorMessage); ok {
                    resp.Err = errMsg // Convert api error into go error
                    return nil
                }
                if !resp.IsSuccessState() {
                    // Neither a success response nor a error response, record details to help troubleshooting
                    resp.Err = fmt.Errorf("bad status: %s\nraw content:\n%s", resp.Status, resp.Dump())
                }
                return nil
            }),
    }
}

type UserProfile struct {
    Name string `json:"name"`
    Blog string `json:"blog"`
}

// GetUserProfile_Style1 returns the user profile for the specified user.
// Github API doc: https://docs.github.com/en/rest/users/users#get-a-user
func (c *GithubClient) GetUserProfile_Style1(ctx context.Context, username string) (user *UserProfile, err error) {
    _, err = c.R().
        SetContext(ctx).
        SetPathParam("username", username).
        SetSuccessResult(&user).
        Get("/users/{username}")
    return
}

// GetUserProfile_Style2 returns the user profile for the specified user.
// Github API doc: https://docs.github.com/en/rest/users/users#get-a-user
func (c *GithubClient) GetUserProfile_Style2(ctx context.Context, username string) (user *UserProfile, err error) {
    err = c.Get("/users/{username}").
        SetPathParam("username", username).
        Do(ctx).
        Into(&user)
    return
}