hackajur

README

README

Getting started

Before running the application you will need a working PostgreSQL installation and a valid DSN (data source name) for connecting to the database.

Please open the cmd/api/main.go file and edit the db-dsn command-line flag to include your valid DSN as the default value.

flag.StringVar(&cfg.db.dsn, "db-dsn", "YOUR DEFAULT DSN GOES HERE", "postgreSQL DSN")

Note that this DSN must be in the format user:pass@localhost:port/db and not be prefixed with postgres://.

Make sure that you're in the root of the project directory, fetch the dependencies with go mod tidy, then run the application using go run ./cmd/api:

$ go mod tidy
$ go run ./cmd/api

If you make a request to the GET /status endpoint using curl you should get a response like this:

$ curl -i localhost:4444/status
HTTP/1.1 200 OK
Content-Type: application/json
Date: Mon, 09 May 2022 20:46:37 GMT
Content-Length: 23

{
    "Status": "OK",
}

Project structure

Everything in the codebase is designed to be editable. Feel free to change and adapt it to meet your needs.

assets	Contains the non-code assets for the application.
↳ assets/emails/	Contains email templates.
↳ assets/migrations/	Contains SQL migrations.
↳ assets/efs.go	Declares an embedded filesystem containing all the assets.

cmd/api	Your application-specific code (handlers, routing, middleware, helpers) for dealing with HTTP requests and responses.
↳ cmd/api/context.go	Contains helpers for working with request context.
↳ cmd/api/errors.go	Contains helpers for managing and responding to error conditions.
↳ cmd/api/handlers.go	Contains your application HTTP handlers.
↳ cmd/api/main.go	The entry point for the application. Responsible for parsing configuration settings initializing dependencies and running the server. Start here when you're looking through the code.
↳ cmd/api/middleware.go	Contains your application middleware.
↳ cmd/api/routes.go	Contains your application route mappings.
↳ cmd/api/server.go	Contains a helper functions for starting and gracefully shutting down the server.

internal	Contains various helper packages used by the application.
↳ internal/database/	Contains your database-related code (setup, connection and queries).
↳ internal/funcs/	Contains custom template functions.
↳ internal/password/	Contains helper functions for hashing and verifying passwords.
↳ internal/request/	Contains helper functions for decoding JSON requests.
↳ internal/response/	Contains helper functions for sending JSON responses.
↳ internal/smtp/	Contains a SMTP sender implementation.
↳ internal/validator/	Contains validation helpers.
↳ internal/version/	Contains the application version number definition.

Configuration settings

Configuration settings are managed via command-line flags in main.go.

You can try this out by using the --http-port flag to configure the network port that the server is listening on:

$ go run ./cmd/api --http-port=9999

Feel free to adapt the run() function to parse additional command-line flags and store their values in the config struct. For example, to add a configuration setting to enable a 'debug mode' in your application you could do this:

type config struct {
    httpPort  int
    debug     bool
}

...

func run() {
    var cfg config

    flag.IntVar(&cfg.httpPort, "http-port", 4444, "port to listen on for HTTP requests")
    flag.BoolVar(&cfg.debug, "debug", false, "enable debug mode")

    flag.Parse()

    ...
}

Creating new handlers

Handlers are defined as http.HandlerFunc methods on the application struct. They take the pattern:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    // Your handler logic...
}

Handlers are defined in the cmd/api/handlers.go file. For small applications, it's fine for all handlers to live in this file. For larger applications (10+ handlers) you may wish to break them out into separate files.

Handler dependencies

Any dependencies that your handlers have should be initialized in the run() function cmd/api/main.go and added to the application struct. All of your handlers, helpers and middleware that are defined as methods on application will then have access to them.

You can see an example of this in the cmd/api/main.go file where we initialize a new logger instance and add it to the application struct.

Creating new routes

chi version 5 is used for routing. Routes are defined in the routes() method in the cmd/api/routes.go file. For example:

func (app *application) routes() http.Handler {
    mux := chi.NewRouter()

    mux.Get("/your/path", app.yourHandler)

    return mux
}

For more information about chi and example usage, please see the official documentation.

Adding middleware

Middleware is defined as methods on the application struct in the cmd/api/middleware.go file. Feel free to add your own. They take the pattern:

func (app *application) yourMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Your middleware logic...
        next.ServeHTTP(w, r)
    })
}

You can then register this middleware with the router using the Use() method:

func (app *application) routes() http.Handler {
    mux := chi.NewRouter()
    mux.Use(app.yourMiddleware)

    mux.Get("/your/path", app.yourHandler)

    return mux
}

It's possible to use middleware on specific routes only by creating route 'groups':

func (app *application) routes() http.Handler {
    mux := chi.NewRouter()
    mux.Use(app.yourMiddleware)

    mux.Get("/your/path", app.yourHandler)

    mux.Group(func(mux chi.Router) {
        mux.Use(app.yourOtherMiddleware)

        mux.Get("/your/other/path", app.yourOtherHandler)
    })

    return mux
}

Note: Route 'groups' can also be nested.

Sending JSON responses

JSON responses and a specific HTTP status code can be sent using the response.JSON() function. The data parameter can be any JSON-marshalable type.

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    data := map[string]string{"hello":  "world"}

    err := response.JSON(w, http.StatusOK, data)
    if err != nil {
        app.serverError(w, r, err)
    }
}

Specific HTTP headers can optionally be sent with the response too:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    data := map[string]string{"hello":  "world"}

    headers := make(http.Header)
    headers.Set("X-Server", "Go")

    err := response.JSONWithHeaders(w, http.StatusOK, data, headers)
    if err != nil {
        app.serverError(w, r, err)
    }
}

Parsing JSON requests

HTTP requests containing a JSON body can be decoded using the request.DecodeJSON() function. For example, to decode JSON into an input struct:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    var input struct {
        Name string `json:"Name"`
        Age  int    `json:"Age"`
    }

    err := request.DecodeJSON(w, r, &input)
    if err != nil {
        app.badRequest(w, r, err)
        return
    }

    ...
}

Note: The target decode destination passed to request.DecodeJSON() (which in the example above is &input) must be a non-nil pointer.

The request.DecodeJSON() function returns friendly, well-formed, error messages that are suitable to be sent directly to the client using the app.badRequest() helper.

There is also a request.DecodeJSONStrict() function, which works in the same way as request.DecodeJSON() except it will return an error if the request contains any JSON fields that do not match a name in the the target decode destination.

Validating JSON requests

The internal/validator package includes a simple (but powerful) validator.Validator type that you can use to carry out validation checks.

Extending the example above:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    var input struct {
        Name      string              `json:"Name"`
        Age       int                 `json:"Age"`
        Validator validator.Validator `json:"-"`
    }

    err := request.DecodeJSON(w, r, &input)
    if err != nil {
        app.badRequest(w, r, err)
        return
    }This codebase has been generated by [Autostrada](https://autostrada.dev/).

    input.Validator.CheckField(input.Name != "", "Name", "Name is required")
    input.Validator.CheckField(input.Age != 0, "Age", "Age is required")
    input.Validator.CheckField(input.Age >= 21, "Age", "Age must be 21 or over")

    if input.Validator.HasErrors() {
        app.failedValidation(w, r, input.Validator)
        return
    }

    ...
}

The app.failedValidation() helper will send a 422 status code along with any validation error messages. For the example above, the JSON response will look like this:

{
    "FieldErrors": {
        "Age": "Age must be 21 or over",
        "Name": "Name is required"
    }
}

In the example above we use the CheckField() method to carry out validation checks for specific fields. You can also use the Check() method to carry out a validation check that is not related to a specific field. For example:

input.Validator.Check(input.Password == input.ConfirmPassword, "Passwords do not match")

The validator.AddError() and validator.AddFieldError() methods also let you add validation errors directly:

input.Validator.AddFieldError("Email", "This email address is already taken")
input.Validator.AddError("Passwords do not match")

The internal/validator/helpers.go file also contains some helper functions to simplify validations that are not simple comparison operations.

NotBlank(value string)	Check that the value contains at least one non-whitespace character.
MinRunes(value string, n int)	Check that the value contains at least n runes.
MaxRunes(value string, n int)	Check that the value contains no more than n runes.
Between(value, min, max T)	Check that the value is between the min and max values inclusive.
Matches(value string, rx *regexp.Regexp)	Check that the value matches a specific regular expression.
In(value T, safelist ...T)	Check that a value is in a 'safelist' of specific values.
AllIn(values []T, safelist ...T)	Check that all values in a slice are in a 'safelist' of specific values.
NotIn(value T, blocklist ...T)	Check that the value is not in a 'blocklist' of specific values.
NoDuplicates(values []T)	Check that a slice does not contain any duplicate (repeated) values.
IsEmail(value string)	Check that the value has the formatting of a valid email address.
IsURL(value string)	Check that the value has the formatting of a valid URL.

For example, to use the Between check your code would look similar to this:

input.Validator.CheckField(validator.Between(input.Age, 18, 30), "Age", "Age must between 18 and 30")

Feel free to add your own helper functions to the internal/validator/helpers.go file as necessary for your application.

Working with the database

This codebase is set up to use PostgreSQL with the lib/pq driver. You can control which database you connect to using the --db-dsn command-line flag to pass in a DSN, or by adapting the default value in run().

The codebase is also configured to use jmoiron/sqlx, so you have access to the whole range of sqlx extensions as well as the standard library Exec(), Query() and QueryRow() methods .

The database is available to your handlers, middleware and helpers via the application struct. If you want, you can access the database and carry out queries directly. For example:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    ...

    _, err := app.db.Exec("INSERT INTO people (name, age) VALUES ($1, $2)", "Alice", 28)
    if err != nil {
        app.serverError(w, r, err)
        return
    }

    ...
}

Generally though, it's recommended to isolate your database logic in the internal/database package and extend the DB type to include your own methods. For example, you could create a internal/database/people.go file containing code like:

type Person struct {
    ID    int    `db:"id"`
    Name  string `db:"name"`
    Age   int    `db:"age"`
}

func (db *DB) NewPerson(name string, age int) error {
    _, err := db.Exec("INSERT INTO people (name, age) VALUES ($1, $2)", name, age)
    return err
}

func (db *DB) GetPerson(id int) (Person, error) {
    var person Person
    err := db.Get(&person, "SELECT * FROM people WHERE id = $1", id)
    return person, err
}

And then call this from your handlers:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    ...

    err := app.db.NewPerson("Alice", 28)
    if err != nil {
        app.serverError(w, r, err)
        return
    }

    ...
}

Managing SQL migrations

The Makefile in the project root contains commands to easily create and work with database migrations:

$ make migrations/new name=add_example_table	Create a new database migration in the assets/migrations folder.
$ make migrations/up	Apply all up migrations.
$ make migrations/down	Apply all down migrations.
$ make migrations/goto version=N	Migrate up or down to a specific migration (where N is the migration version number).
$ make migrations/force version=N	Force the database to be specific version without running any migrations.
$ make migrations/version	Display the currently in-use migration version.

Hint: You can run $ make help at any time for a reminder of these commands.

These Makefile tasks are simply wrappers around calls to the github.com/golang-migrate/migrate/v4/cmd/migrate tool. For more information, please see the official documentation.

By default all 'up' migrations are automatically run on application startup using embeded files from the assets/migrations directory. You can disable this by setting the --db-automigrate command-line flag to false.

Logging

Leveled logging is supported using the slog package.

By default, a logger is initialized in the main() function. This logger writes all log messages above Debug level to os.Stdout.

logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelDebug}))

Feel free to customize this further as necessary.

Also note: Any messages that are automatically logged by the Go http.Server are output at the Warn level.

Sending emails

The application is configured to support sending of emails via SMTP.

Email templates should be defined as files in the assets/emails folder. Each file should contain named templates for the email subject, plaintext body and — optionally — HTML body.

{{define "subject"}}Example subject{{end}}

{{define "plainBody"}}
This is an example body
{{end}}

{{define "htmlBody"}}
<!doctype html>
<html>
    <head>
        <meta name="viewport" content="width=device-width" />
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    </head>
    <body>
        <p>This is an example body</p>
    </body>
</html>
{{end}}

A further example can be found in the assets/emails/example.tmpl file. Note that your email templates automatically have access to the custom template functions defined in the internal/funcs package.

Emails can be sent from your handlers using app.mailer.Send(). For example, to send an email to alice@example.com containing the contents of the assets/emails/example.tmpl file:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    ...

    data := map[string]any{"Name": "Alice"}

    err := app.mailer.Send("alice@example.com", data, "example.tmpl")
    if err != nil {
        app.serverError(w, r, err)
        return
    }

   ...
}

Note: The second parameter to Send() should be a map or struct containing any dynamic data that you want to render in the email template.

The SMTP host, port, username, password and sender details can be configured using the --smtp-host command-line flag, --smtp-port command-line flag, --smtp-username command-line flag, --smtp-password command-line flag, and --smtp-from command-line flag or by adapting the default values in cmd/api/main.go.

You may wish to use Mailtrap or a similar tool for development purposes.

Custom template functions

Custom template functions are defined in internal/funcs/funcs.go and are automatically made available to your

email templates when you use app.mailer.Send() .

The following custom template functions are already included by default:

now	Returns the current time.
timeSince arg1	Returns the time elapsed since arg1.
timeUntil arg2	Returns the time until arg1.
formatTime arg1 arg2	Returns the time arg2 as formatted using the pattern arg1.
approxDuration arg1	Returns the approximate duration of arg1 in a 'human-friendly' format ("3 seconds", "2 months", "5 years") etc.
uppercase arg1	Returns arg1 converted to uppercase.
lowercase arg1	Returns arg1 converted to lowercase.
pluralize arg1 arg2 arg3	If arg1 equals 1 then return arg2, otherwise return arg3.
slugify arg1	Returns the lowercase of arg1 with all non-ASCII characters and punctuation removed (expect underscores and hyphens). Whitespaces are also replaced with a hyphen.
safeHTML arg1	Output the verbatim value of arg1 without escaping the content. This should only be used when arg1 is from a trusted source.
join arg1 arg2	Returns the values in slice arg1 joined using the separator arg2.
incr arg1	Increments arg1 by 1.
decr arg1	Decrements arg1 by 1.
formatInt arg1	Returns arg1 formatted with commas as the thousands separator.
formatFloat arg1 arg2	Returns arg1 rounded to arg2 decimal places and formatted with commas as the thousands separator.
yesno arg1	Returns "Yes" if arg1 is true, or "No" if arg1 is false.
urlSetParam arg1 arg2 arg3	Returns the URL arg1 with the key arg2 and value arg3 added to the query string parameters.
urlDelParam arg1 arg2	Returns the URL arg1 with the key arg2 (and corresponding value) removed from the query string parameters.

To add another custom template function, define the function in internal/funcs/funcs.go and add it to the TemplateFuncs map. For example:

var TemplateFuncs = template.FuncMap{
    ...
    "yourFunction": yourFunction,
}

func yourFunction(s string) (string, error) {
    // Do something...
}

User accounts

The application is configured to support user accounts with fully-functional signup and authentication workflows.

A User struct describing the data for a user is defined in internal/database/users.go.

type User struct {
    ID             int       `db:"id"`
    Created        time.Time `db:"created"`
    Email          string    `db:"email"`
    HashedPassword string    `db:"hashed_password"`
}

Feel free to add additional fields to this struct (don't forget to also update the SQL queries, migrations, and handler code as necessary!).

A new user account can be created by sending a request to the POST /users endpoint:

$ curl -i -d '{"Email": "alice@example.com", "Password": "sectr3t_pa55word"}' localhost:4444/users
HTTP/1.1 204 No Content
Vary: Authorization
Date: Wed, 17 Aug 2022 05:18:12 GMT

Authentication is managed using stateless tokens. When running the application you should use your own secret key for signing the tokens. This key should be a random 32-character string generated using a CSRNG which you pass to the application using the --jwt-secret command-line flag:

$ go run ./cmd/api --jwt-secret-key=a1uiBXkmY03pxXok3OkFV39saE8Cn574

A new authentication token can be created by sending the user's email and password to the POST /authentication-tokens endpoint.

$ curl -i -d '{"Email": "alice@example.com", "Password": "sectr3t_pa55word"}' localhost:4444/authentication-tokens
HTTP/1.1 200 OK
Content-Type: application/json
Vary: Authorization
Date: Wed, 17 Aug 2022 05:26:02 GMT
Content-Length: 353

{
    "AuthenticationToken": "eyJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJodHRwOi8vbG9jYWxob3N0OjQ0NDQiLCJzdWIiOiIxIiwiYXVkIjpbImh0dHA6Ly9sb2NhbGhvc3Q6NDQ0NCJdLCJleHAiOjE2NjA4MDAzNjIuMjc0MDU2MiwibmJmIjoxNjYwNzEzOTYyLjI3NDA1NjcsImlhdCI6MTY2MDcxMzk2Mi4yNzQwNTY0fQ.t469-8hrwyZUN8gWmK5TeelXgstFnwBaoW977F2JbrE",
    "AuthenticationTokenExpiry": "2022-08-18T07:26:02+02:00"
}

The authentication token is a JWT containing the user's ID. By default authentication tokens are valid for 24 hours. You can change this by editing the code in the createAuthenticationToken handler.

Subsequent requests to the API should include the authentication token in a HTTP Authorization header in the following format:

Authorization: Bearer <authentication token>

The authenticate middleware is used to check for the presence of an Authorization header. If the token is valid, the token is decoded and the user information is fetched from the database. You can retrieve the details of the current user in your application handlers by calling the contextGetAuthenticatedUser() helper.

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    ...

    authenticatedUser := contextGetAuthenticatedUser(r)

    ...
}

If an Authorization header is provided with a request but it is invalid or expired, then the authenticate middleware will return a 401 Unauthorized response and an error message to the client.

If no Authorization header is provided, then the request is coming from an unauthenticated client. In this case, the authenticate middleware will not return an error, but calls to the contextGetAuthenticatedUser() helper function will return nil.

You can restrict access to specific handlers based on whether a request is coming from an authenticated client by using the requireAuthenticatedUser middleware. An example of using this can be seen in the cmd/app/routes.go file.

Important: You should only call the requireAuthenticatedUser middleware after the authenticate middleware.

Admin tasks

The Makefile in the project root contains commands to easily run common admin tasks:

$ make tidy	Format all code using go fmt and tidy the go.mod file.
$ make audit	Run go vet, staticheck, govulncheck, execute all tests and verify required modules.
$ make test	Run all tests.
$ make test/cover	Run all tests and outputs a coverage report in HTML format.
$ make build	Build a binary for the cmd/api application and store it in the /tmp/bin folder.
$ make run	Build and then run a binary for the cmd/api application.

Running background tasks

A backgroundTask() helper is included in the cmd/api/helpers.go file. You can call this in your handlers, helpers and middleware to run any logic in a separate background goroutine. This useful for things like sending emails, or completing slow-running jobs.

You can call it like so:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    ...

    app.backgroundTask(r, func() error {
        // The logic you want to execute in a background task goes here.
        // It should return an error, or nil.
        err := doSomething()
        if err != nil {
            return err
        }

        return nil
    })

    ...
}

Using the backgroundTask() helper will automatically recover any panics in the background task logic, and when performing a graceful shutdown the application will wait for any background tasks to finish running before it exits.

Application version

The application version number is generated automatically based on your latest version control system revision number. If you are using Git, this will be your latest Git commit hash. It can be retrieved by calling the version.Get() function from the internal/version package.

Important: The version control system revision number will only be available when the application is built using go build. If you run the application using go run then version.Get() will return the string "unavailable".