Go: Get path parameters from http.Request

I'm developing a REST API with Go, but I don't know how can I do the path mappings and retrieve the path parameters from them.

I want something like this:

func main() {
	http.HandleFunc("/provisions/:id", Provisions) //<-- How can I map "id" parameter in the path?
	http.ListenAndServe(":8080", nil)
}

func Provisions(w http.ResponseWriter, r *http.Request) {
    //I want to retrieve here "id" parameter from request
}

I would like to use just http package instead of web frameworks, if it is possible.

Thanks.

If you don't want to use any of the multitude of the available routing packages, then you need to parse the path yourself:

Route the /provisions path to your handler

http.HandleFunc("/provisions/", Provisions)

Then split up the path as needed in the handler

id := strings.TrimPrefix(req.URL.Path, "/provisions/")
// or use strings.Split, or use regexp, etc.

You can use golang gorilla/mux package's router to do the path mappings and retrieve the path parameters from them.

import (
    "fmt"
    "github.com/gorilla/mux"
    "net/http"
)

func main() {
    r := mux.NewRouter()
    r.HandleFunc("/provisions/{id}", Provisions)
    http.ListenAndServe(":8080", r)
}

func Provisions(w http.ResponseWriter, r *http.Request) {
    vars := mux.Vars(r)
    id, ok := vars["id"]
    if !ok {
	    fmt.Println("id is missing in parameters")
    }
    fmt.Println(`id := `, id)
    //call http://localhost:8080/provisions/someId in your browser
    //Output : id := someId
}

Golang read value from URL query "/template/get/123".

I used standard gin routing and handling request parameters from context parameters.

Use this in registering your endpoint:

func main() {
    r := gin.Default()
    g := r.Group("/api")
    {
        g.GET("/template/get/:Id", templates.TemplateGetIdHandler)
    }
    r.Run()
}

And use this function in handler

func TemplateGetIdHandler(c *gin.Context) {
	req := getParam(c, "Id")
    //your stuff
}

func getParam(c *gin.Context, paramName string) string {
	return c.Params.ByName(paramName)
}

Golang read value from URL query "/template/get?id=123".

Use this in registering your endpoint:

func main() {
    r := gin.Default()
    g := r.Group("/api")
    {
        g.GET("/template/get", templates.TemplateGetIdHandler)
    }
    r.Run()
}

And use this function in handler

type TemplateRequest struct {
	Id string `form:"id"`
}

func TemplateGetIdHandler(c *gin.Context) {
    var request TemplateRequest
    err := c.Bind(&request)
    if err != nil {
	    log.Println(err.Error())
	    c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
    }
    //your stuff
}

You can do this with standard library handlers. Note http.StripPrefix accepts an http.Handler and returns a new one:

func main() {
  mux := http.NewServeMux()
  provisionsPath := "/provisions/"
  mux.Handle(
    provisionsPath,
    http.StripPrefix(provisionsPath, http.HandlerFunc(Provisions)),
  )
}

func Provisions(w http.ResponseWriter, r *http.Request) {
  fmt.Println("Provision ID:", r.URL.Path)
}

See working demo on Go playground.

You can also nest this behavior using submuxes; http.ServeMux implements http.Handler, so you can pass one into http.StripPrefix just the same.