finish the polling thing

main.go

@@ -7,6 +7,7 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"os/signal"
 	"time"
 
 	_ "github.com/lib/pq"
@@ -163,6 +164,39 @@ func fetchWeather(apiKey, city string) (WeatherResponse, error) {
 	return weather, nil
 }
 
+func startPoller(db *sql.DB, apiKey, city string, interval time.Duration) {
+	weather, err := fetchWeather(apiKey, city)
+	if err != nil {
+		log.Printf("poller: fetch failed: %v", err)
+	} else {
+		id, err := saveReading(db, weather)
+		if err != nil {
+			log.Printf("poller: save failed %v", err)
+		} else {
+			log.Printf("poller: saved reading #%d for %s (%.1f F)", id, weather.Name, weather.Main.Temp)
+		}
+	}
+
+	ticker := time.NewTicker(interval)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		weather, err := fetchWeather(apiKey, city)
+		if err != nil {
+			log.Printf("poller fetch failed: %v", err)
+			continue // don't crash
+		}
+
+		id, err := saveReading(db, weather)
+		if err != nil {
+			log.Printf("poller: save failed: %v", err)
+			continue
+		}
+		log.Printf("poller: saved reading #%d for %s (%.1f F)", id, weather.Name, weather.Main.Temp)
+	}
+
+}
+
 func main() {
 	apiKey := getEnv("OPENWEATHERMAP_API_KEY")
 	defaultCity := getEnv("WEATHER_CITY")
@@ -172,6 +206,9 @@ func main() {
 
 	createTable(db)
 
+	// Start background polling in a goroutine
+	go startPoller(db, apiKey, defaultCity, 10*time.Minute)
+
 	// POST /weather/fetch?city=London - fetch current weather and save it
 	http.HandleFunc("/weather/fetch", func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
@@ -228,8 +265,17 @@ func main() {
 		json.NewEncoder(w).Encode(readings)
 	})
 
-	port := ":8080"
-	fmt.Printf("server listening on %s\n", port)
-	log.Fatal(http.ListenAndServe(port, nil))
+	go func() {
+		fmt.Println("server listening on :8080")
+		if err := http.ListenAndServe(":8080", nil); err != nil {
+			log.Fatalf("server failed: %v", err)
+		}
+	}()
+
+	// wait for Ctrl+C
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, os.Interrupt)
+	<-quit
+	fmt.Println("\nshutting down...")
 
 }