├── .gitignore
├── README.md
└── main.go


/.gitignore:
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 1 | how-i-start-go
 2 | 
 3 | # Compiled Object files, Static and Dynamic libs (Shared Objects)
 4 | *.o
 5 | *.a
 6 | *.so
 7 | 
 8 | # Folders
 9 | _obj
10 | _test
11 | 
12 | # Architecture specific extensions/prefixes
13 | *.[568vq]
14 | [568vq].out
15 | 
16 | *.cgo1.go
17 | *.cgo2.c
18 | _cgo_defun.c
19 | _cgo_gotypes.go
20 | _cgo_export.*
21 | 
22 | _testmain.go
23 | 
24 | *.exe
25 | *.test
26 | 


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/README.md:
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1 | # How I start Go
2 | 
3 | This repository holds the code that we build in the
4 | [How I Start](http://www.howistart.org/) article about
5 | [Go](http://www.howistart.org/posts/go/1).
6 | 
7 | 


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/main.go:
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  1 | package main
  2 | 
  3 | import (
  4 | 	"encoding/json"
  5 | 	"flag"
  6 | 	"log"
  7 | 	"net/http"
  8 | 	"strings"
  9 | 	"time"
 10 | )
 11 | 
 12 | func main() {
 13 | 	openWeatherMapAPIKey := flag.String("openweathermap.api.key", "0123456789abcdef", "openweathermap.org API key")
 14 | 	wundergroundAPIKey := flag.String("wunderground.api.key", "0123456789abcdef", "wunderground.com API key")
 15 | 	flag.Parse()
 16 | 
 17 | 	mw := multiWeatherProvider{
 18 | 		openWeatherMap{apiKey: *openWeatherMapAPIKey},
 19 | 		weatherUnderground{apiKey: *wundergroundAPIKey},
 20 | 	}
 21 | 
 22 | 	http.HandleFunc("/weather/", func(w http.ResponseWriter, r *http.Request) {
 23 | 		begin := time.Now()
 24 | 		city := strings.SplitN(r.URL.Path, "/", 3)[2]
 25 | 
 26 | 		temp, err := mw.temperature(city)
 27 | 		if err != nil {
 28 | 			http.Error(w, err.Error(), http.StatusInternalServerError)
 29 | 			return
 30 | 		}
 31 | 
 32 | 		w.Header().Set("Content-Type", "application/json; charset=utf-8")
 33 | 		json.NewEncoder(w).Encode(map[string]interface{}{
 34 | 			"city": city,
 35 | 			"temp": temp,
 36 | 			"took": time.Since(begin).String(),
 37 | 		})
 38 | 	})
 39 | 
 40 | 	http.ListenAndServe(":8080", nil)
 41 | }
 42 | 
 43 | type weatherProvider interface {
 44 | 	temperature(city string) (float64, error) // in Kelvin, naturally
 45 | }
 46 | 
 47 | type multiWeatherProvider []weatherProvider
 48 | 
 49 | func (w multiWeatherProvider) temperature(city string) (float64, error) {
 50 | 	// Make a channel for temperatures, and a channel for errors.
 51 | 	// Each provider will push a value into only one.
 52 | 	temps := make(chan float64, len(w))
 53 | 	errs := make(chan error, len(w))
 54 | 
 55 | 	// For each provider, spawn a goroutine with an anonymous function.
 56 | 	// That function will invoke the temperature method, and forward the response.
 57 | 	for _, provider := range w {
 58 | 		go func(p weatherProvider) {
 59 | 			k, err := p.temperature(city)
 60 | 			if err != nil {
 61 | 				errs <- err
 62 | 				return
 63 | 			}
 64 | 			temps <- k
 65 | 		}(provider)
 66 | 	}
 67 | 
 68 | 	sum := 0.0
 69 | 
 70 | 	// Collect a temperature or an error from each provider.
 71 | 	for i := 0; i < len(w); i++ {
 72 | 		select {
 73 | 		case temp := <-temps:
 74 | 			sum += temp
 75 | 		case err := <-errs:
 76 | 			return 0, err
 77 | 		}
 78 | 	}
 79 | 
 80 | 	// Return the average, same as before.
 81 | 	return sum / float64(len(w)), nil
 82 | }
 83 | 
 84 | type openWeatherMap struct {
 85 | 	apiKey string
 86 | }
 87 | 
 88 | func (w openWeatherMap) temperature(city string) (float64, error) {
 89 | 	resp, err := http.Get("http://api.openweathermap.org/data/2.5/weather?APPID=" + w.apiKey + "&q=" + city)
 90 | 	if err != nil {
 91 | 		return 0, err
 92 | 	}
 93 | 
 94 | 	defer resp.Body.Close()
 95 | 
 96 | 	var d struct {
 97 | 		Main struct {
 98 | 			Kelvin float64 `json:"temp"`
 99 | 		} `json:"main"`
100 | 	}
101 | 
102 | 	if err := json.NewDecoder(resp.Body).Decode(&d); err != nil {
103 | 		return 0, err
104 | 	}
105 | 
106 | 	log.Printf("openWeatherMap: %s: %.2f", city, d.Main.Kelvin)
107 | 	return d.Main.Kelvin, nil
108 | }
109 | 
110 | type weatherUnderground struct {
111 | 	apiKey string
112 | }
113 | 
114 | func (w weatherUnderground) temperature(city string) (float64, error) {
115 | 	resp, err := http.Get("http://api.wunderground.com/api/" + w.apiKey + "/conditions/q/" + city + ".json")
116 | 	if err != nil {
117 | 		return 0, err
118 | 	}
119 | 
120 | 	defer resp.Body.Close()
121 | 
122 | 	var d struct {
123 | 		Observation struct {
124 | 			Celsius float64 `json:"temp_c"`
125 | 		} `json:"current_observation"`
126 | 	}
127 | 
128 | 	if err := json.NewDecoder(resp.Body).Decode(&d); err != nil {
129 | 		return 0, err
130 | 	}
131 | 
132 | 	kelvin := d.Observation.Celsius + 273.15
133 | 	log.Printf("weatherUnderground: %s: %.2f", city, kelvin)
134 | 	return kelvin, nil
135 | }
136 | 


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