跨平台应用开发的新革命：掌握Go语言的技巧和策略

package main

import "golang.org/x/mobile/app"

func main() {
    app.Run(app.Callbacks{})
}

package db

import (
    "database/sql"
    _ "github.com/mattn/go-sqlite3"
)

type DB interface {
    Connect() error
    GetUserById(id int) *User
    // ...
}

type User struct {
    Id       int
    Username string
    // ...
}

type SQLiteDB struct {
    conn *sql.DB
}

func (db *SQLiteDB) Connect() error {
    // Connect to SQLite database
}

func (db *SQLiteDB) GetUserById(id int) *User {
    // Query user by id from SQLite database
}

package main

import (
    "fmt"
    "io/ioutil"
    "net/http"
)

func main() {
    urls := []string{
        "http://example.com/image1.jpg",
        "http://example.com/image2.jpg",
        "http://example.com/image3.jpg",
    }

    for _, url := range urls {
        go downloadImage(url)
    }

    // Wait for all goroutines to finish
    fmt.Println("All images downloaded!")
}

func downloadImage(url string) {
    resp, err := http.Get(url)
    if err != nil {
        fmt.Println("Error downloading image:", err)
        return
    }
    defer resp.Body.Close()

    data, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        fmt.Println("Error reading image data:", err)
        return
    }

    // Save image to local disk
    // ...
}