选题: 20180712 Building a Messenger App: Development Login

sources/tech/20180712 Building a Messenger App- Development Login.md

sources/tech/20180712 Building a Messenger App- Development Login.md

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+[#]: collector: (lujun9972)
+[#]: translator: ( )
+[#]: reviewer: ( )
+[#]: publisher: ( )
+[#]: url: ( )
+[#]: subject: (Building a Messenger App: Development Login)
+[#]: via: (https://nicolasparada.netlify.com/posts/go-messenger-dev-login/)
+[#]: author: (Nicolás Parada https://nicolasparada.netlify.com/)
+
+Building a Messenger App: Development Login
+======
+
+This post is the 6th on a series:
+
+  * [Part 1: Schema][1]
+  * [Part 2: OAuth][2]
+  * [Part 3: Conversations][3]
+  * [Part 4: Messages][4]
+  * [Part 5: Realtime Messages][5]
+
+
+
+We already implemented login through GitHub, but if we want to play around with the app, we need a couple of users to test it. In this post we’ll add an endpoint to login as any user just giving an username. This endpoint will be just for development.
+
+Start by adding this route in the `main()` function.
+
+```
+router.HandleFunc("POST", "/api/login", requireJSON(login))
+```
+
+### Login
+
+This function handles POST requests to `/api/login` with a JSON body with just an username and returns the authenticated user, a token and expiration date of it in JSON format.
+
+```
+func login(w http.ResponseWriter, r *http.Request) {
+    if origin.Hostname() != "localhost" {
+        http.NotFound(w, r)
+        return
+    }
+
+    var input struct {
+        Username string `json:"username"`
+    }
+    if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+        http.Error(w, err.Error(), http.StatusBadRequest)
+        return
+    }
+    defer r.Body.Close()
+
+    var user User
+    if err := db.QueryRowContext(r.Context(), `
+        SELECT id, avatar_url
+        FROM users
+        WHERE username = $1
+    `, input.Username).Scan(
+        &user.ID,
+        &user.AvatarURL,
+    ); err == sql.ErrNoRows {
+        http.Error(w, "User not found", http.StatusNotFound)
+        return
+    } else if err != nil {
+        respondError(w, fmt.Errorf("could not query user: %v", err))
+        return
+    }
+
+    user.Username = input.Username
+
+    exp := time.Now().Add(jwtLifetime)
+    token, err := issueToken(user.ID, exp)
+    if err != nil {
+        respondError(w, fmt.Errorf("could not create token: %v", err))
+        return
+    }
+
+    respond(w, map[string]interface{}{
+        "authUser":  user,
+        "token":     token,
+        "expiresAt": exp,
+    }, http.StatusOK)
+}
+```
+
+First it checks we are on localhost or it responds with `404 Not Found`. It decodes the body skipping validation since this is just for development. Then it queries to the database for a user with the given username, if none is found, it returns with `404 Not Found`. Then it issues a new JSON web token using the user ID as Subject.
+
+```
+func issueToken(subject string, exp time.Time) (string, error) {
+    token, err := jwtSigner.Encode(jwt.Claims{
+        Subject:    subject,
+        Expiration: json.Number(strconv.FormatInt(exp.Unix(), 10)),
+    })
+    if err != nil {
+        return "", err
+    }
+    return string(token), nil
+}
+```
+
+The function does the same we did [previously][2]. I just moved it to reuse code.
+
+After creating the token, it responds with the user, token and expiration date.
+
+### Seed Users
+
+Now you can add users to play with to the database.
+
+```
+INSERT INTO users (id, username) VALUES
+    (1, 'john'),
+    (2, 'jane');
+```
+
+You can save it to a file and pipe it to the Cockroach CLI.
+
+```
+cat seed_users.sql | cockroach sql --insecure -d messenger
+```
+
+* * *
+
+That’s it. Once you deploy the code to production and use your own domain this login function won’t be available.
+
+This post concludes the backend.
+
+[Souce Code][6]
+
+--------------------------------------------------------------------------------
+
+via: https://nicolasparada.netlify.com/posts/go-messenger-dev-login/
+
+作者：[Nicolás Parada][a]
+选题：[lujun9972][b]
+译者：[译者ID](https://github.com/译者ID)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]: https://nicolasparada.netlify.com/
+[b]: https://github.com/lujun9972
+[1]: https://nicolasparada.netlify.com/posts/go-messenger-schema/
+[2]: https://nicolasparada.netlify.com/posts/go-messenger-oauth/
+[3]: https://nicolasparada.netlify.com/posts/go-messenger-conversations/
+[4]: https://nicolasparada.netlify.com/posts/go-messenger-messages/
+[5]: https://nicolasparada.netlify.com/posts/go-messenger-realtime-messages/
+[6]: https://github.com/nicolasparada/go-messenger-demo