APIを叩いてJSONにするところまで

go_openweathermap_sample.go

package main

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

const API_KEY = "xxxxxxxxxxxxxxx"
const BASE_URL = "http://api.openweathermap.org/data/2.5/weather"

type Weather struct {
    Id          int    `json:"id"`
    Main        string `json:"main"`
    Description string `json:"description"`
}

type WeatherJson struct {
  Weather []Weather `json:"weather"`
}

func main()  {
  url := BASE_URL + "?"+ "q=tokyo&units=metric" + "&appid=" + API_KEY
  resp, err := http.Get(url)

  if err != nil {
    fmt.Println(err)
    return
  }

  defer resp.Body.Close()

  byteArray, err := ioutil.ReadAll(resp.Body)

  if err != nil {
    fmt.Println(err)
    return
  }

  weatherJson := new(WeatherJson)
  if err := json.Unmarshal(byteArray, weatherJson); err != nil {
    fmt.Println(err)
    return
  }

  fmt.Println(weatherJson.Weather[0].Id) // ex. 803
  fmt.Println(weatherJson.Weather[0].Main) // ex. Clouds
  fmt.Println(weatherJson.Weather[0].Description) // ex. broken clouds
}