chi for Go: A Complete Guide with Examples

What is chi and why is it needed?

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chi is a lightweight, high-performance, and idiomatic HTTP router for the Go programming language. It is designed for developing web applications and APIs, providing developers with a powerful and flexible tool for routing HTTP requests.

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Unlike the standard net/http package, chi offers:

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• Compatibility with net/http: chi fully implements the http.Handler interface, making it easy to integrate with existing Go code and middleware.
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• Context-based routing: chi uses context.Context to pass route parameters (e.g., user ID) between middleware and handlers.
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• Nested routes (Subrouters): Allows grouping routes into logical blocks (e.g., /api/v1/users).
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• Middleware grouping: Middleware can be applied to the entire router or to individual route groups.
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• Built-in support for CORS, logging, compression, and other common tasks.
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chi is ideal for building REST APIs, microservices, and any web applications requiring a clean, performant, and easily testable architecture.

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Installing chi

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To install chi, use the standard Go package manager. Make sure you have Go installed (version 1.14 or higher).

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go get -u github.com/go-chi/chi/v5

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After running this command, the library will be added to your go.mod file. If you are using Go Modules (recommended), the import will look like this:

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import "github.com/go-chi/chi/v5"

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It is also common to install the middleware package:

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go get -u github.com/go-chi/cors\ngo get -u github.com/go-chi/chi/v5/middleware

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Quick Start with a Code Example

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Let's create a simple HTTP server that responds to GET requests.

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package main\n\nimport (\n    "fmt"\n    "net/http"\n\n    "github.com/go-chi/chi/v5"\n)\n\nfunc main() {\n    r := chi.NewRouter()\n\n    // Define a route\n    r.Get("/hello", func(w http.ResponseWriter, r *http.Request) {\n        fmt.Fprintf(w, "Hello, chi!")\n    })\n\n    // Start the server\n    http.ListenAndServe(":3000", r)\n}

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Run this code and open your browser to http://localhost:3000/hello. You will see the message "Hello, chi!".

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Main chi Methods and Functions

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Let's look at the key methods of the chi library. All examples assume you have already created a router r := chi.NewRouter().

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1. Get(pattern string, handlerFn http.HandlerFunc)

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What it does: Registers a handler for the HTTP GET method at the specified path pattern.

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Parameters:

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• pattern — a path string (e.g., /users, /users/{id}).
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• handlerFn — a handler function matching the http.HandlerFunc signature.
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Example:

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r.Get("/", func(w http.ResponseWriter, r *http.Request) {\n    w.Write([]byte("Home page"))\n})

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2. Post(pattern string, handlerFn http.HandlerFunc)

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What it does: Registers a handler for the HTTP POST method.

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Parameters: Similar to Get.

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Example:

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r.Post("/users", func(w http.ResponseWriter, r *http.Request) {\n    // Logic for creating a user\n    w.WriteHeader(http.StatusCreated)\n    w.Write([]byte("User created"))\n})

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3. Put(pattern string, handlerFn http.HandlerFunc)

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What it does: