go_flutter_counter

README

README

This codebase has been generated by Autostrada.

Getting started

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",
}

You can also start the application with live reload support by using the run task in the Makefile:

$ make run

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/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/errors.go	Contains helpers for managing and responding to error conditions.
↳ cmd/api/handlers.go	Contains your application HTTP handlers.
↳ cmd/api/helpers.go	Contains helper functions for common tasks.
↳ 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/cookies	Contains helper functions for reading/writing signed and encrypted cookies.
↳ internal/database/	Contains your database-related code (setup, connection and queries).
↳ internal/env	Contains helper functions for reading configuration settings from environment variables.
↳ internal/request/	Contains helper functions for decoding JSON requests.
↳ internal/response/	Contains helper functions for sending JSON responses.
↳ internal/validator/	Contains validation helpers.
↳ internal/version/	Contains the application version number definition.

Configuration settings

Configuration settings are managed via environment variables, with the environment variables read into your application in the run() function in the main.go file.

You can try this out by setting a HTTP_PORT environment variable to configure the network port that the server is listening on:

$ export HTTP_PORT="9999"
$ go run ./cmd/api

Feel free to adapt the run() function to parse additional environment variables and store their values in the config struct. The application uses helper functions in the internal/env package to parse environment variable values or return a default value if no matching environment variable is set. It includes env.GetString(), env.GetInt() and env.GetBool() functions for reading string, integer and bool values from environment variables. Again, you can add any additional helper functions that you need.

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
    }

    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 SQLite3 with the mattn/go-sqlite3 driver. The data is stored in a db.sqlite file in the project root, but you can change this by setting a different DSN (datasource name) in the DB_DSN environment variable , 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 environment variable to false.

Important: If you change your database location from the default db.sqlite file then you will need to also update the Makefile tasks to reference the new location.

Logging

Leveled logging is supported using the slog and tint packages.

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(tint.NewHandler(os.Stdout, &tint.Options{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.

Cookies

The internal/cookies package provides helper functions for reading and writing cookies.

The Write() function base64-encodes the cookie value and checks the cookie length is no more than 4096 bytes before writing the cookie. You can use it like this:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    // Initialize a Go cookie as normal.
    cookie := http.Cookie{
        Name:     "exampleCookie",
        Value:    "Hello Zoë!",
        Path:     "/",
        MaxAge:   3600,
        HttpOnly: true,
        Secure:   true,
        SameSite: http.SameSiteLaxMode,
    }

    // Write the cookie.
    err := cookies.Write(w, cookie)
    if err != nil {
        app.serverError(w, r, err)
        return
    }

    ...
}

The Read() function reads a named cookie and base64-decodes the value before returning it.

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    // Read the cookie value and handle any errors as necessary for your application.
    value, err := cookies.Read(r, "exampleCookie")
    if err != nil {
        switch {
        case errors.Is(err, http.ErrNoCookie):
            app.badRequest(w, r, err)
        case errors.Is(err, cookies.ErrInvalidValue):
            app.badRequest(w, r, err)
        default:
            app.serverError(w, r, err)
        }
        return
    }

    ...
}

The internal/cookies package also provides WriteSigned() and ReadSigned() functions for writing/reading signed cookies, and WriteEncrypted() and ReadEncrypted() functions encrypted cookies. Signed cookies are authenticated using HMAC-256, meaning that you can trust that the contents of the cookie has not been tampered with. Encrypted cookies are encrpyted using AES-GCM, which both authenticates and encrypts the cookie data, meaning that you can trust that the contents of the cookie has not been tampered with and the contents of the cookie cannot be read by the client.

When using these helper functions, you must set your own (secret) key for signing and encryption. This key should be a random 32-character string generated using a CSRNG which you pass to the application using the COOKIE_SECRET_KEY environment variable. For example:

$ export COOKIE_SECRET_KEY="heoCDWSgJ430OvzyoLNE9mVV9UJFpOWx"
$ go run ./cmd/api

To write a new signed or encrypted cookie:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    // Initialize a Go cookie as normal.
    cookie := http.Cookie{
        Name:     "exampleCookie",
        Value:    "Hello Zoë!",
        Path:     "/",
        MaxAge:   3600,
        HttpOnly: true,
        Secure:   true,
        SameSite: http.SameSiteLaxMode,
    }

    // Write a signed cookie using WriteSigned() and passing in the secret key
    // as the final argument. Use WriteEncrypted() if you want an encrpyted
    // cookie instead.
    err := cookies.WriteSigned(w, cookie, app.config.cookie.secretKey)
    if err != nil {
        app.serverError(w, r, err)
        return
    }

    ...
}

To read a signed or encrypted cookie:

func (app *application) yourHandler(w http.ResponseWriter, r *http.Request) {
    // Read the cookie value using ReadSigned() and passing in the secret key
    // as the final argument. Use ReadEncrypted() if you want to read an
    // encrpyted cookie instead.
    value, err := cookies.ReadSigned(r, "exampleCookie", app.config.cookie.secretKey)
    if err != nil {
        switch {
        case errors.Is(err, http.ErrNoCookie):
            app.badRequest(w, r, err)
        case errors.Is(err, cookies.ErrInvalidValue):
            app.badRequest(w, r, err)
        default:
            app.serverError(w, r, err)
        }
        return
    }

    ...
}

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.
$ make run/live	Build and then run a binary for the cmd/api application (uses live reloading).

Live reload

When you use make run/live to run the application, the application will automatically be rebuilt and restarted whenever you make changes to any files with the following extensions:

.go
.tpl, .tmpl, .html
.css, .js, .sql
.jpeg, .jpg, .gif, .png, .bmp, .svg, .webp, .ico

Behind the scenes the live reload functionality uses the cosmtrek/air tool. You can configure how it works (including which file extensions and folders are watched for changes) by editing the Makefile file.

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 after you have initialized version control for your repository (e.g. run $ git init) AND application is built using go build. If you run the application using go run then version.Get() will return the string "unavailable".

Changing the module path

The module path is currently set to github.com/crossevol/go_flutter_counter. If you want to change this please find and replace all instances of github.com/crossevol/go_flutter_counter in the codebase with your own module path.