Consuming REST api

rest-api.go

package main

import (
  "encoding/json"
  "fmt"
  "io"
  "io/ioutil"
  "net/http"
  "strconv"
  "strings"
)

const addr = "localhost:7070"

type City struct {
  ID       string
  Name     string `json:"name"`
  Location string `json:"location"`
}

func (c City) toJson() string {
  return fmt.Sprintf(`{"name":"%s","location":"%s"}`,
    c.Name,
    c.Location)
}

func main() {
  s := createServer(addr)
  go s.ListenAndServe()

  cities, err := getCities()
  if err != nil {
    panic(err)
  }
  fmt.Printf("Retrived cities: %v\n", cities)

  city, err := saveCity(City{"", "Paris", "France"})
  if err != nil {
    panic(err)
  }
  fmt.Printf("Saved city: %v\n", city)

}

func saveCity(city City) (City, error) {
  r, err := http.Post("http://"+addr+"/cities",
    "application/json",
    strings.NewReader(city.toJson()))
  if err != nil {
    return City{}, err
  }
  defer r.Body.Close()
  return decodeCity(r.Body)
}

func getCities() ([]City, error) {
  r, err := http.Get("http://" + addr + "/cities")
  if err != nil {
    return nil, err
  }
  defer r.Body.Close()
  return decodeCities(r.Body)
}

func decodeCity(r io.Reader) (City, error) {
  city := City{}
  dec := json.NewDecoder(r)
  err := dec.Decode(&city)
  return city, err
}

func decodeCities(r io.Reader) ([]City, error) {
  cities := []City{}
  dec := json.NewDecoder(r)
  err := dec.Decode(&cities)
  return cities, err
}

func createServer(addr string) http.Server {
  cities := []City{City{"1", "Prague", "Czechia"}, City{"2", "Bratislava", "Slovakia"}}
  mux := http.NewServeMux()
  mux.HandleFunc("/cities", func(w http.ResponseWriter, r *http.Request) {
    enc := json.NewEncoder(w)
    if r.Method == http.MethodGet {
      enc.Encode(cities)
    } else if r.Method == http.MethodPost {
      data, err := ioutil.ReadAll(r.Body)
      if err != nil {
        http.Error(w, err.Error(), 500)
      }
      r.Body.Close()
      city := City{}
      json.Unmarshal(data, &city)
      city.ID = strconv.Itoa(len(cities) + 1)
      cities = append(cities, city)
      enc.Encode(city)
    }

  })
  return http.Server{
    Addr:    addr,
    Handler: mux,
  }
}