Parsing URL Query Parameters

A minimal example of parsing query parameters on get requests

This is a small example of how to parse url query parameters in Go. I was learning this in service of another project, in which case I wanted the parameters in the map[string]string format, but this doesn’t always need to be the case.

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"
    "strings"
)

func DemoGet(w http.ResponseWriter, r *http.Request) {

    urlParams := r.URL.Query()

    //in a use case for another project, i want the urlParams to be encoded as a map[string]string
    //but this won't always be the use case
    m := make(map[string]string, len(urlParams))

    for i, v := range urlParams {
        //in prod, we probably don't want to error out
        //but yolo for now
        if len(v) > 1 {
            log.Fatal("query parameters should all be length 1")
        }
        s := strings.Join(v, "")
        m[i] = s
    }

    w.Header().Set("Content-Type", "application/json")

    json.NewEncoder(w).Encode(m)
}

func main() {
    r := http.NewServeMux()

    r.HandleFunc("/demoget", DemoGet)

    s := &http.Server{
        Addr:    ":8080",
        Handler: r,
    }

    fmt.Println("Running demo program")

    s.ListenAndServe()
}