main.go

package main

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

func main() {
	http.HandleFunc("/hardcoded", textHandle)
	http.HandleFunc("/json_api", jsonHandle)
	log.Fatal(http.ListenAndServe(":8080", nil))
}

func textHandle(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "foo")
}

func jsonHandle(w http.ResponseWriter, r *http.Request) {
	j := struct {
		Foo string `json:"foo"`
	}{
		"bar",
	}

	json.NewEncoder(w).Encode(&j)
}