Introduction

Serve static files from a specific directory (system physical or embedded to the application) is done by the Party.HandleDir method.
HandleDir registers a handler that serves HTTP requests with the contents of a file system (physical or embedded).
First parameter  : the route path
Second parameter : the file system that needs to be served
Third parameter  : optional, the directory options.
HandleDir(requestPath string, fs http.FileSystem, opts ...DirOptions) ( []*Route)
The DirOptions structure looks like this:
type DirOptions struct {
    // Defaults to "/index.html", if request path is ending with **/*/$IndexName
    // then it redirects to **/*(/).
    // That index handler is registered automatically
    // by the framework unless but it can be overriden.
    IndexName string
    // PushTargets filenames (map's value) to
    // be served without additional client's requests (HTTP/2 Push)
    // when a specific request path (map's key WITHOUT prefix)
    // is requested and it's not a directory (it's an `IndexFile`).
    //
    // Example:
    //     "/": {
    //         "favicon.ico",
    //         "js/main.js",
    //         "css/main.css",
    //     }
    PushTargets map[string][]string
    // PushTargetsRegexp like `PushTargets` but accepts regexp which
    // is compared against all files under a directory (recursively).
    // The `IndexName` should be set.
    //
    // Example:
    // "/": regexp.MustCompile("((.*).js|(.*).css|(.*).ico)$")
    // See `iris.MatchCommonAssets` too.
    PushTargetsRegexp map[string]*regexp.Regexp
​
    // Cache to enable in-memory cache and pre-compress files.
    Cache DirCacheOptions
    // When files should served under compression.
    Compress bool
​
    // List the files inside the current requested
    // directory if `IndexName` not found.
    ShowList bool
    // If `ShowList` is true then this function will be used instead
    // of the default one to show the list of files of
    // a current requested directory(dir).
    // See `DirListRich` package-level function too.
    DirList DirListFunc
​
    // Files downloaded and saved locally.
    Attachments Attachments
​
    // Optional validator that loops through each requested resource.
    AssetValidator func(ctx *context.Context, name string) bool
}
Quick Start
Let's say that you have an ./assets folder near to your executable and you want the files to be served through http://localhost:8080/static/**/* route.
app := iris.New()
​
app.HandleDir("/static", iris.Dir("./assets"))
​
app.Listen(":8080")
Now, if you want to embed the static files to be lived inside the executable build in order to not depend on a system directory you can use a tool like go-bindata to convert the files into []byte inside your program. Let's take a quick tutorial on this and how Iris helps to serve those data.
Install go-bindata:
$ go get -u github.com/go-bindata/go-bindata/v3/go-bindata
Navigate to your program directory, that the ./assets subdirectory exists and execute:
$ go-bindata -fs -prefix "assets" ./assets/...
The above creates a generated go file which contains a AssetFile() functions that returns a compatible http.FileSystem you can give to Iris to serve the files.
// [app := iris.New...]
​
app.HandleDir("/static", AssetFile())
Run your app:
$ go run .
The HandleDir supports all the standards, including content-range, for both physical, embedded and cached directories.
However, if you just need a handler to work with, without register a route, you can use the iris.FileServer package-level function instead.
The FileServer function returns a Handler which serves files from a specific system directory, an embedded one or a memory-cached one.
iris.FileServer(fs http.FileSystem, options DirOptions)
Usage
handler := iris.FileServer(iris.Dir("./assets"), iris.DirOptions {
    ShowList: true, Compress: true, IndexName: "index.html",
})
Example
Let's create an application that users can upload one or more files and list them.
Copy-paste the contents of main.go:
package main
​
import (
    "crypto/md5"
    "fmt"
    "io"
    "mime/multipart"
    "os"
    "strconv"
    "strings"
    "time"
​
    "github.com/kataras/iris/v12"
)
​
func init() {
    os.Mkdir("./uploads", 0700)
}
​
func main() {
    app := iris.New()
    app.RegisterView(iris.HTML("./views", ".html"))
    // Serve assets (e.g. javascript, css).
    app.HandleDir("/public", iris.Dir("./public"))
​
    app.Get("/", index)
​
    app.Get("/upload", uploadView)
    app.Post("/upload", upload)
​
    app.HandleDir("/files", iris.Dir("./uploads"), iris.DirOptions{
        Compress: true,
        ShowList: true,
    })
​
    app.Listen(":8080")
}
​
func index(ctx iris.Context) {
    ctx.Redirect("/upload")
}
​
func uploadView(ctx iris.Context) {
    now := time.Now().Unix()
    h := md5.New()
    io.WriteString(h, strconv.FormatInt(now, 10))
    token := fmt.Sprintf("%x", h.Sum(nil))
​
    ctx.View("upload.html", token)
}
​
const maxSize = 10 * iris.MB
​
func upload(ctx iris.Context) {
    ctx.SetMaxRequestBodySize(maxSize)
​
    _, err := ctx.UploadFormFiles("./uploads", beforeSave)
    if err != nil {
        ctx.StopWithError(iris.StatusPayloadTooRage, err)
        return
    }
​
    ctx.Redirect("/files")
}
​
func beforeSave(ctx iris.Context, file *multipart.FileHeader) {
    ip := ctx.RemoteAddr()
    ip = strings.ReplaceAll(ip, ".", "_")
    ip = strings.ReplaceAll(ip, ":", "_")
​
    file.Filename = ip + "-" + file.Filename
}
The ./views/upload.html is a simple html form, looks like that:
<!DOCTYPE html>
<html lang="en">
​
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Upload Files</title>
</head>
​
<body>
    <form enctype="multipart/form-data" action="/upload" method="POST">
        <input type="file" id="upload_files" name="upload_files" multiple />
        <input type="hidden" name="token" value="{{.}}" />
​
        <input type="button" value="Upload Using JS" onclick="uploadFiles()" />
        <input type="submit" value="Upload by submiting the form" />
    </form>
​
    <script type="text/javascript">
        function uploadFiles() {
            let files = document.getElementById("upload_files").files;
            let formData = new FormData();
            for (var i = 0; i < files.length; i++) {
                formData.append("files[]", files[i]);
            }
​
            fetch('/upload',
                {
                    method: "POST",
                    body: formData
                }).
                then(data => window.location = "/files").
                catch(e => window.alert("upload failed: file too large"));
        }
    </script>
</body>
​
</html>
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