Query Parameters in Go

query parameters in Go using the net/http package

To retrieve query parameters in Go using the net/http package, you can use the URL.Query() method of the http.Request object. This method returns a url.Values map, which allows you to easily access query parameters by their key.

Here’s an example:

package main

import (
  "fmt"
  "net/http"
)

func handler(w http.ResponseWriter, r *http.Request) {
  // Parse query parameters
  queryParams := r.URL.Query()

  // Retrieve specific parameters
  param1 := queryParams.Get("param1") // Get a single value for the "param1" key
  param2 := queryParams.Get("param2")

  // Print them to the response
  fmt.Fprintf(w, "param1: %s\n", param1)
  fmt.Fprintf(w, "param2: %s\n", param2)

  // Optional: Iterate over all query parameters
  for key, values := range queryParams {
    for _, value := range values {
      fmt.Fprintf(w, "Key: %s, Value: %s\n", key, value)
    }
  }
}

func main() {
  http.HandleFunc("/", handler)

  fmt.Println("Server is running on http://localhost:8080")
  http.ListenAndServe(":8080", nil)
}

Explanation:

1. r.URL.Query():

   • Returns the query parameters as a url.Values map, where each key maps to a slice of strings (map[string][]string).

2. queryParams.Get("key"):

   • Fetches the first value associated with the given key.

3. Iteration:

   • If you want to handle multiple values for a single key, iterate over the slice.

Example Query:

If the URL is http://localhost:8080/?param1=value1&param2=value2&param1=value3, the output will be:

param1: value1
param2: value2
Key: param1, Value: value1
Key: param1, Value: value3
Key: param2, Value: value2

---

path parameters in Go using the net/http package

you can get path parames with r.PathValue("param-name")

url example http://localhost:8080/{user}/{post}/{id}

package main

import (
  "fmt"
  "net/http"
)

func main() {
  http.HandleFunc("/users/{id}", handler)
  http.ListenAndServe(":8080", nil)
}

func handler(w http.ResponseWriter, r *http.Request) {
  // you can get path parames with r.PathValue("param-name")
  id := r.PathValue("id")
  fmt.Printf("User ID: %s\n", id)
  fmt.Fprintf(w, "User ID: %s\n", id)
}