Learning Go - Build your first Slack app using Go and App Engine

Transcript

1. Learning Go Build your first Slack app using Go and App Engine
2. 1. Why Go? 2. Learning the basics of Go 3. Deploying to App Engine 4. Building our Slack app
3. Building HTTP APIs in Go is extremely easy
4. Why go?
5. Go is what C++ should have been @ernesto_jimenez's joke
6. 272 pages
7. 1.368 pages just C++?
8. 400 pages
10. it is very simple
11. and very powerful
12. it has great tooling
13. and the stdlib is amazing
14. You can be productive with go really quickly
15. Why am I here?
18. The very basics
19. Hello World
20. package main import "fmt" func main() { fmt.Println("Hello DevFest!") }
21. $ go run main.go Hello DevFest!
22. Hello World API
23. package main import ( "fmt" "net/http" ) func main() { http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { name := r.URL.Query().Get("name") if name == "" { name = "DevFest" } fmt.Fprintf(w, "Hello %s!", name) }) http.ListenAndServe(":8080", http.DefaultServeMux) }
24. $ curl http://localhost:8080/ Hello DevFest! $ curl "http://localhost:8080/?name=world" Hello world!
25. Hello World JSON API
26. package main import ( "encoding/json" "fmt" "net/http" )
27. type request struct { Name string `json:"name"` } type response struct { Message string `json:"message,omitempty"` Error string `json:"error,omitempty"` }
28. func main() { http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { var data request err := json.NewDecoder(r.Body).Decode(&data) if err != nil { w.WriteHeader(http.StatusBadRequest) json.NewEncoder(w).Encode(response{ Error: err.Error(), }) return } json.NewEncoder(w).Encode(response{ Message: fmt.Sprintf("Hello %s!", data.Name), }) }) http.ListenAndServe(":8080", http.DefaultServeMux) }
29. $ curl http://localhost:8080/ -d '{"name": "DevFest"}' {"message":"Hello DevFest!"} $ curl http://localhost:8080/ -d 'Something' {"error":"invalid character 'S' looking for beginning of value"}
30. Deploying to App Engine
31. Create your app.yaml
32. runtime: go api_version: go1 handlers: - url: /.* script: _go_app
33. Tweak your code
34. package app // rename your package import ( "encoding/json" "fmt" "net/http" ) func init() { // change main for init http.HandleFunc("/", handler) // remove http.ListenAndServe } func handler(w http.ResponseWriter, r *http.Request) { // ... }
35. Install the Go App Engine SDK https://cloud.google.com/appengine/downloads
36. Run your API locally
37. $ goapp serve Skipping SDK update check. Starting API server at: http://localhost:63885 Starting module "default" running at: http://localhost:8080 Starting admin server at: http://localhost:8000 default: "POST / HTTP/1.1" 200 29 $ curl http://localhost:8080/ -d '{"name": "DevFest"}' {"message":"Hello DevFest!"}
39. Deploying your application
40. Create a Google Cloud Project https://console.cloud.google.com/ save your project id
41. $ goapp deploy \ --application [ YOUR PROJECT ID ] \ --version [ OPTIONAL VERSION ID ] \ app.yaml
42. $ goapp deploy \ --application devfest-bot \ --version hello-world \ app.yaml
43. $ curl http://hello-world.devfest-bot.appspot.com/ \ -d '{"name": "DevFest"}' {"message":"Hello DevFest!"}
44. Building our Slack app
46. token=uitkEUWQ9mLLyNZPKsitLjGE team_id=T0001 team_domain=example channel_id=C2147483705 channel_name=test user_id=U2147483697 user_name=Steve command=/weather text=London response_url=https://hooks.slack.com/commands/1234/5678
47. /echo
48. package echo import ( "fmt" "net/http" ) func init() { http.HandleFunc("/command", command) } func command(w http.ResponseWriter, r *http.Request) { user := r.PostFormValue("user_name") text := r.PostFormValue("text") fmt.Fprintf(w, "%s, %s", user, text) }
49. Testing it out locally
50. $ goapp serve $ ngrok http 8080 Web Interface http://127.0.0.1:4040 Forwarding http://274a0d24.ngrok.io -> localhost:8080 Forwarding https://274a0d24.ngrok.io -> localhost:8080
54. Deploying
55. $ goapp deploy \ --application devfest-bot \ --version echo \ app.yaml
60. Securing the command
61. go get google.golang.org/appengine
62. import ( "fmt" "net/http" "os" "google.golang.org/appengine" "google.golang.org/appengine/log" )
63. func init() { http.HandleFunc("/command", checkToken(os.Getenv("TOKEN"), command)) } func checkToken(token string, h http.HandlerFunc) http.HandlerFunc { return func(w http.ResponseWriter, r *http.Request) { ctx := appengine.NewContext(r) if r.PostFormValue("token") != token { log.Warningf(ctx, "Invalid token") w.WriteHeader(http.StatusUnauthorized) return } h(w, r) } } func command(w http.ResponseWriter, r *http.Request) { user := r.PostFormValue("user_name") text := r.PostFormValue("text") fmt.Fprintf(w, "%s, %s", user, text) }
64. $ appcfg.py update \ --application devfest-bot \ --version echo \ -E TOKEN:[ YOUR TOKEN ] \ app.yaml
65. $ curl -iX POST http://echo.devfest-bot.appspot.com/command \ -d token=invalid HTTP/1.1 401 Unauthorized Content-Type: text/html; charset=utf-8 X-Cloud-Trace-Context: 249651e6b5324a76026990575350b6b4;o=1 Date: Sun, 02 Oct 2016 17:31:55 GMT Server: Google Frontend Content-Length: 0
66. /translate
67. go get google.golang.org/api/translate/v2
68. import ( "fmt" "net/http" "os" "google.golang.org/appengine" "google.golang.org/appengine/log" "google.golang.org/api/googleapi/transport" "google.golang.org/api/translate/v2" "google.golang.org/appengine/urlfetch" )
69. var apiKey = os.Getenv("TRANSLATE_KEY") func command(w http.ResponseWriter, r *http.Request) { ctx := appengine.NewContext(r) ts, err := translate.New(&http.Client{ Transport: &transport.APIKey{ Key: apiKey, Transport: &urlfetch.Transport{Context: ctx}, }, }) if err != nil { log.Errorf(ctx, "Error translate.New: %s", err.Error()) http.Error(w, "internal error", http.StatusInternalServerError) return } // ...
70. // ... t := ts.Translations.List([]string{ r.PostFormValue("text"), }, "en") res, err := t.Do() if err != nil { log.Errorf(ctx, "Error translating: %s", err.Error()) fmt.Fprintf(w, "Error: %s", err.Error()) return } for _, t := range res.Translations { text := t.TranslatedText lang := t.DetectedSourceLanguage fmt.Fprintf(w, "%s (%s)\n", text, lang) } }
73. A nicer output
74. type message struct { Text string `json:"text"` Attachments []attachment `json:"attachments,omitempty"` ResponseType string `json:"response_type,omitempty"` } type attachment struct { Text string `json:"text"` Color string `json:"color"` }
75. func command(w http.ResponseWriter, r *http.Request) { // [ initialise ts ] w.Header().Set("Content-Type", "application/json") t := ts.Translations.List([]string{r.PostFormValue("text")}, "en") res, err := t.Do() if err != nil { log.Errorf(ctx, "Error translating: %s", err.Error()) json.NewEncoder(w).Encode(message{ Text: "Error", Attachments: []attachment{ {Color: "danger", Text: err.Error()}, }, }) return } // ...
76. // ... msg := message{ Text: fmt.Sprintf("Translating %q", r.PostFormValue("text")), ResponseType: "in_channel", } for _, t := range res.Translations { msg.Attachments = append(msg.Attachments, attachment{ Color: "good", Text: fmt.Sprintf( "%s (%s)", t.TranslatedText, t.DetectedSourceLanguage, ), }) } json.NewEncoder(w).Encode(msg) }
78. under 100 lines of code
79. production ready
80. the source code git.io/devfest-london-2016
81. the Slack invite.slack.golangbridge.org #golang-newbies
82. Happy Hacking! @ernesto_jimenez ernesto@slackline.io