Parse a JSON http POST in GoLang

parse_json_post.go

package main

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

type test_struct struct {
	Test string
}

func parseGhPost(rw http.ResponseWriter, request *http.Request) {
	decoder := json.NewDecoder(request.Body)

	var t test_struct
	err := decoder.Decode(&t)

	if err != nil {
		panic(err)
	}

	fmt.Println(t.Test)
}

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

Don't forget

defer r.Body.Close()

Example

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
        "time"

	"github.com/gorilla/mux"
)

type player struct {
	Name string
	Club string
	Age  uint8
}

func mainLogic(w http.ResponseWriter, r *http.Request) {
	if r.Method == "POST" {
		var tempPlayer player
		decoder := json.NewDecoder(r.Body)
		err := decoder.Decode(&tempPlayer)

		if err != nil {
			panic(err)
		}
		defer r.Body.Close()

		fmt.Printf("Got %s age %d club %s\n", tempPlayer.Name, tempPlayer.Age, tempPlayer.Club)
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(tempPlayer)
	} else {
		w.WriteHeader(http.StatusMethodNotAllowed)
		w.Write([]byte("Method not allowed."))
	}
}

func main() {
	r := mux.NewRouter()

	r.HandleFunc("/", mainLogic).Methods("POST")
	srv := &http.Server{
		Handler:      r,
		Addr:         "localhost:8000",
		WriteTimeout: 15 * time.Second,
		ReadTimeout:  15 * time.Second,
	}

	log.Fatal(srv.ListenAndServe())
}

Go JSON content-type using the middleware

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"time"

	"github.com/gorilla/mux"
)

type player struct {
	Name string
	Club string
	Age  uint8
}

func middleware(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Println("Executing Content-type middleware before the request phase!")

		if r.Header.Get("Content-type") != "application/json" {
			w.WriteHeader(http.StatusUnsupportedMediaType)
			w.Write([]byte("415 - Unsupported Media Type. Only JSON files are allowed"))
			return
		}

		// Pass control back to the handler
		handler.ServeHTTP(w, r)
	})
}

func mainLogic(w http.ResponseWriter, r *http.Request) {
	// Business logic here
	if r.Method == "POST" {
		fmt.Println("INSIDE LOGIC")
		var tempPlayer player
		decoder := json.NewDecoder(r.Body)
		err := decoder.Decode(&tempPlayer)

		if err != nil {
			panic(err)
		}
		defer r.Body.Close()

		fmt.Printf("Got %s age %d club %s\n", tempPlayer.Name, tempPlayer.Age, tempPlayer.Club)
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(tempPlayer)
	} else {
		w.WriteHeader(http.StatusMethodNotAllowed)
		w.Write([]byte("Method not allowed."))
	}
}

func main() {
	r := mux.NewRouter()

	r.HandleFunc("/", mainLogic).Methods("POST")
	r.Use(middleware)

	srv := &http.Server{
		Handler:      r,
		Addr:         "localhost:8000",
		WriteTimeout: 15 * time.Second,
		ReadTimeout:  15 * time.Second,
	}

	log.Fatal(srv.ListenAndServe())
}

A simple middleware function to check if the POST request is in JSON format.

invalid character 't' looking for beginning of object key string

I fixed it by replacing first and last double quotes to single quotes: -d "{"test": "that"}" -> -d '{"test": "that"}'

Thank you. It helped me to resolved issue.