如何使用Golang，Gin和Postgresql构建CRUD应用程序

<code>crud-app/
├── main.go            # 应用入口
├── config/
│   └── database.go    # 数据库连接配置
├── controllers/
│   └── item.go        # "item"资源的CRUD处理程序
├── models/
│   └── item.go        # "item"数据库模型
├── routes/
│   └── routes.go      # API路由定义
├── go.mod             # Go模块文件
└── go.sum             # 依赖文件</code>

<code class="bash">mkdir crud-app
cd crud-app
go mod init github.com/yourusername/crud-app</code>

<code class="bash">go get github.com/gin-gonic/gin
go get github.com/jackc/pgx/v5</code>

<code class="sql">CREATE DATABASE crud_app;

\c crud_app

CREATE TABLE items (
    id SERIAL PRIMARY KEY,
    name TEXT NOT NULL,
    description TEXT,
    price NUMERIC(10, 2)
);</code>

<code class="go">package config

import (
    "database/sql"
    "fmt"
    "log"

    _ "github.com/jackc/pgx/v5/stdlib"
)

var db *sql.DB

func ConnectDatabase() {
    var err error
    dsn := "postgres://username:password@localhost:5432/crud_app"
    db, err = sql.Open("pgx", dsn)
    if err != nil {
        log.Fatalf("无法连接到数据库: %v", err)
    }

    fmt.Println("数据库连接成功!")
}</code>

<code class="go">package models

type Item struct {
    ID          int     `json:"id"`
    Name        string  `json:"name"`
    Description string  `json:"description"`
    Price       float64 `json:"price"`
}</code>

<code class="go">package controllers

import (
    "crud-app/config"
    "crud-app/models"
    "github.com/gin-gonic/gin"
    "net/http"
)

// 创建新的item
func CreateItem(c *gin.Context) {
    var item models.Item
    if err := c.ShouldBindJSON(&item); err != nil {
        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
        return
    }

    query := "INSERT INTO items (name, description, price) VALUES ($1, $2, $3) RETURNING id"
    err := config.db.QueryRow(query, item.Name, item.Description, item.Price).Scan(&item.ID)
    if err != nil {
        c.JSON(http.StatusInternalServerError, gin.H{"error": "创建item失败"})
        return
    }

    c.JSON(http.StatusCreated, item)
}</code>

<code class="go">package routes

import (
    "crud-app/controllers"
    "github.com/gin-gonic/gin"
)

func SetupRoutes(router *gin.Engine) {
    router.POST("/items", controllers.CreateItem)
    // 添加更多路由用于读取、更新、删除
}</code>

<code class="go">package main

import (
    "crud-app/config"
    "crud-app/routes"
    "github.com/gin-gonic/gin"
)

func main() {
    config.ConnectDatabase()

    r := gin.Default()
    routes.SetupRoutes(r)

    r.Run(":8080") // 在8080端口启动服务器
}</code>

<code class="bash">go run main.go</code>

<code class="json">{
  "name": "Laptop",
  "description": "一台强大的笔记本电脑",
  "price": 1200.50
}</code>