GeezerVison

Writing a basic HTTP server is easy using the net/http package.

package main

import (
    "fmt"
    "net/http"
)

A fundamental concept in net/http servers is handlers. A handler is an object implementing the http.Handler interface. A common way to write a handler is by using the http.HandlerFunc adapter on functions with the appropriate signature.

func hello(w http.ResponseWriter, req *http.Request) {

Functions serving as handlers take a http.ResponseWriter and a http.Request as arguments. The response writer is used to fill in the HTTP response. Here our simple response is just “hello\n”.

    fmt.Fprintf(w, "hello\n")
}

func headers(w http.ResponseWriter, req *http.Request) {

This handler does something a little more sophisticated by reading all the HTTP request headers and echoing them into the response body.

    for name, headers := range req.Header {
        for _, h := range headers {
            fmt.Fprintf(w, "%v: %v\n", name, h)
        }
    }
}

func main() {

We register our handlers on server routes using the http.HandleFunc convenience function. It sets up the default router in the net/http package and takes a function as an argument.

    http.HandleFunc("/hello", hello)
    http.HandleFunc("/headers", headers)

Finally, we call the ListenAndServe with the port and a handler. nil tells it to use the default router we’ve just set up.

    http.ListenAndServe(":8090", nil)
}

Run the server in the background.

$ go run http-server.go &

Access the /hello route.

$ curl localhost:8090/hello
hello