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A Fluent Go REST Client Library

Fast Shot is a robust, feature-rich, and highly configurable HTTP client for Go. Crafted with modern Go practices in mind, it offers a fluent, chainable API that allows for clean, idiomatic code.

Table of Contents

• Why Fast Shot?
• Features
• Installation
• Quick Start
• Advanced Usage
• Contributing

Why Fast Shot?

• Fluent & Chainable API: Write expressive, readable, and flexible HTTP client code.
• Ease of Use: Reduce boilerplate, making HTTP requests as straightforward as possible.
• Rich Features: From headers to query parameters and JSON support, Fast Shot covers your needs.
• Advanced Retry Mechanism: Built-in support for retries with various backoff strategies.

Features 🌟

• Fluent and chainable API for clean, expressive code
• Comprehensive HTTP method support (GET, POST, PUT, DELETE, etc.)
• Flexible authentication options (Bearer Token, Basic Auth, Custom)
• Easy manipulation of headers, cookies, and query parameters
• Advanced retry mechanism with customizable backoff strategies
• Pre-request and post-response hooks for observability and custom logic
• Client-side load balancing for improved reliability
• JSON request and response support
• XML request and response support
• Timeout and redirect control
• Proxy support
• Extensible and customizable for specific needs
• Well-tested and production-ready

Installation 🔧

Fast Shot requires Go 1.27 or later. To install it, run:

go get github.com/opus-domini/fast-shot

Quick Start 🚀

Here's how you can make a simple POST using Fast Shot:

package main

import (
    "fmt"
    fastshot "github.com/opus-domini/fast-shot"
    "github.com/opus-domini/fast-shot/constant/mime"
)

func main() {
    client := fastshot.NewClient("https://api.example.com").
        Auth().BearerToken("your_token_here").
        Build()

    payload := map[string]any{
        "key1": "value1",
        "key2": "value2",
    }

    response, err := client.POST("/endpoint").
        Header().AddAccept(mime.JSON).
        Body().AsJSON(payload).
        Send()

    // Check for request send problems.
    if err != nil {
        panic(err) // (¬_¬")
    }

    // Check for (4xx || 5xx) errors response.
    if response.Status().IsError() {
        panic(response.Body().AsString()) // ¯\_(ツ)_/¯
    }

    // Decode straight into a typed value (Go 1.27 generic method).
    result, err := response.Body().AsJSON[map[string]any]()

    // Congrats! Do something awesome with the result (¬‿¬)
    fmt.Println(result)
}

Advanced Usage 🤖

Fluent API

Easily chain multiple settings in a single line:

client := fastshot.NewClient("https://api.example.com").
    Auth().BearerToken("your-bearer-token").
    Header().Add("My-Header", "My-Value").
    Config().SetTimeout(30 * time.Second).
    Build()

Advanced Retry Mechanism

Handle transient failures with customizable backoff strategies:

client.POST("/resource").
    Retry().SetExponentialBackoff(2 * time.Second, 5, 2.0).
    Send()

This new retry feature supports:

• Constant backoff
• Exponential backoff
• Full jitter for both constant and exponential backoff
• Custom retry conditions
• Maximum delay setting

Request Hooks

Inject custom logic before sending requests and after receiving responses. Useful for logging, metrics, tracing, request signing, and audit logs:

client := fastshot.NewClient("https://api.example.com").
    Hook().OnBeforeRequest(func(req *http.Request) error {
        req.Header.Set("X-Request-ID", uuid.New().String()) // stdlib uuid, Go 1.27+
        return nil
    }).
    Hook().OnAfterResponse(func(req *http.Request, resp *http.Response) {
        log.Printf("%s %s → %d", req.Method, req.URL, resp.StatusCode)
    }).
    Build()

Hooks can also be set per-request:

client.GET("/resource").
    Hook().OnBeforeRequest(func(req *http.Request) error {
        // Only for this request
        return nil
    }).
    Send()

Key behaviors:

• Client hooks run before request hooks (same ordering as headers and cookies)
• Hooks run on every attempt, including retries
• A before-request hook returning an error aborts the request
• After-response hooks are observational and do not return errors

Generic Response Decoding (Go 1.27)

Skip the pre-allocated destination and decode straight into a typed value:

type User struct {
    Name string `json:"name"`
}

user, err := response.Body().AsJSON[User]()
// also available: response.Body().AsXML[User]()

Pluggable JSON Codec (encoding/json/v2)

Bodies are encoded/decoded with the standard encoding/json/v2 (Go 1.27+): strict, interoperable defaults — invalid UTF-8, duplicate object keys, and trailing data are rejected.

Need the lenient encoding/json (v1) semantics? Opt in:

client := fastshot.NewClient("https://api.example.com").
    Config().SetJSONCodec(fastshot.NewJSONv1Codec()).
    Build()

Bring your own codec by implementing fastshot.JSONCodec (Encode/Decode funcs).

Out-of-the-Box Support for Client Load Balancing

Effortlessly manage multiple endpoints:

client := fastshot.NewClientLoadBalancer([]string{
    "https://api1.example.com",
    "https://api2.example.com",
    "https://api3.example.com",
    }).
    Config().SetTimeout(time.Second * 10).
    Build()

This feature allows you to distribute network traffic across several servers, enhancing the performance and reliability of your applications.

Authentication

Fast Shot supports various types of authentication:

// Bearer Token
builder.Auth().BearerToken("your-bearer-token")

// Basic Authentication
builder.Auth().BasicAuth("username", "password")

// Custom Authentication
builder.Auth().Set("custom-authentication-header")

Custom Headers and Cookies

Add your own headers and cookies effortlessly:

// Add Custom Header
builder.Header().
    Add("header", "value")

// Add Multiple Custom Headers
builder.Header().
    AddAll(map[header.Type]string{
        "key1": "value1",
        "key2": "value2",
        "key3": "value3",
    })

// Add Custom Cookie
builder.Cookie().
    Add(&http.Cookie{Name: "session_id", Value: "id"})

Advanced Configurations

Control every aspect of the HTTP client:

// Set Timeout
builder.Config().
    SetTimeout(time.Second * 30)

// Set Follow Redirect
builder.Config().
    SetFollowRedirects(false)

// Set Custom Transport
builder.Config().
    SetCustomTransport(myCustomTransport)

// Set Proxy
builder.Config().
    SetProxy("http://my-proxy-server:port")

Response Handling

Extract information from the response with ease:

// Fluent response status check
response.Status()

// Easy response body access and conversion
response.Body()

// Get response headers to inspect
response.Header()

// Get response cookies for further processing 
response.Cookie()

// Get raw response if needed
response.Raw()

// and more...

Contributing 🤝

We welcome contributions to Fast Shot! Here's how you can contribute:

1. Fork the repository
2. Create a new branch for your feature or bug fix
3. Write your code and tests
4. Ensure all tests pass
5. Submit a pull request

Please make sure to update tests as appropriate and adhere to the existing coding style.

For more detailed information, check out our CONTRIBUTING.md file.