parse authorization headers in go

main.go
package main

import (
    "encoding/base64"
    "fmt"
    "net/http"
    "strings"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        authHeader := r.Header.Get("Authorization")
        if authHeader != "" {
            // The Authorization header should look like "Basic <base64-encoded string>"
            auth := strings.SplitN(authHeader, " ", 2)
            if len(auth) != 2 || auth[0] != "Basic" {
                http.Error(w, "Invalid Authorization header", http.StatusBadRequest)
                return
            }

            // Decode the base64-encoded string
            payload, err := base64.StdEncoding.DecodeString(auth[1])
            if err != nil {
                http.Error(w, "Invalid Authorization header", http.StatusBadRequest)
                return
            }

            // The payload should look like "<username>:<password>"
            pair := strings.SplitN(string(payload), ":", 2)
            if len(pair) != 2 {
                http.Error(w, "Invalid Authorization header", http.StatusBadRequest)
                return
            }

            // At this point, `pair[0]` is the username and `pair[1]` is the password
            username := pair[0]
            password := pair[1]

            // Do something with the username and password, like authenticate the request
            fmt.Fprintf(w, "Welcome, %s!", username)
        } else {
            // No Authorization header provided
            http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
        }
    })

    http.ListenAndServe(":8080", nil)
}
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