package main

import (
    "fmt"
    "net/http"
)

func main() {
    http.Handle("/", corsMiddleware(http.HandlerFunc(indexHandler)))
    http.ListenAndServe(":8080", nil)
}

func indexHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, "Hello from Go Backend")
}

func corsMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // 設(shè)置 CORS 響應(yīng)頭
        w.Header().Set("Access-Control-Allow-Origin", "*") // 允許所有來(lái)源
        w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
        w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")

        // 如果是預(yù)檢請(qǐng)求，直接返回
        if r.Method == "OPTIONS" {
            w.WriteHeader(http.StatusNoContent)
            return
        }

        // 繼續(xù)處理請(qǐng)求
        next.ServeHTTP(w, r)
    })
}

go get github.com/gin-contrib/cors

package main

import (
    "github.com/gin-contrib/cors"
    "github.com/gin-gonic/gin"
    "time"
)

func main() {
    r := gin.Default()

    // 使用 cors 中間件
    r.Use(cors.New(cors.Config{
        AllowOrigins:     []string{"http://localhost:3000"}, // 只允許特定域名
        AllowMethods:     []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
        AllowHeaders:     []string{"Origin", "Content-Type", "Authorization"},
        ExposeHeaders:    []string{"Content-Length"},
        AllowCredentials: true,
        MaxAge:           12 * time.Hour,
    }))

    r.GET("/", func(c *gin.Context) {
        c.JSON(200, gin.H{"message": "Hello from Gin!"})
    })

    r.Run(":8080")
}