Get Weather Data from Open Weather Map.

weathermap.go

package main

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

type WeatherData struct {
	Weather []struct {
		Description string `json: "description"`
	} `json: "weather"`
	Main struct {
		Temp     float64 `json: "temp"`
		Pressure uint16  `json: "pressure"`
	} `json: "main`
}

func fetchWeather(lat float64, lon float64) WeatherData {
	var data WeatherData

	api_key, hasApiKey := os.LookupEnv("WEATHERMAP_API_KEY")
	if !hasApiKey {
		panic("No API key.")
	}

	url := "https://api.openweathermap.org/data/2.5/weather?lat=%2.1f&lon=%3.1f&appid=%s"

	url = fmt.Sprintf(url, lat, lon, api_key)
	resp, err := http.Get(url)
	if err != nil {
		fmt.Println("Cannot get weather: ", err)
		return data
	}
	defer resp.Body.Close()

	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
		fmt.Println("Cannot get weather: ", err)
		return data
	}
	return data
}

func main() {
	startNow := time.Now()
	lat, lon := 47.4, 7.9
	data := fetchWeather(lat, lon)

	fmt.Printf("%s, %2.1f°C\n", data.Weather[0].Description, data.Main.Temp-273)
	fmt.Println("Took: ", time.Since(startNow))

}