package main

import (
    "github.com/gin-gonic/gin"
    "awesomeProject/app/app_routers"
    "strings"
    "fmt"
    "net/http"
)


/* 路由初始化*/
var (
    engine = gin.Default()
)

func main() {

    // 允许使用跨域请求  全局中间件
    engine.Use(Cors())
    //router.Use(cors.Default())
    // 传参 设定路由组 允许路由组使用路由
    app_routers.Router(engine)
    // 启动路由 设定端口

    engine.Run(":11000")                                                    //运行启动端口

}


func Cors() gin.HandlerFunc {
    return func(c *gin.Context) {
        method := c.Request.Method      //请求方法
        origin := c.Request.Header.Get("Origin")        //请求头部
        var headerKeys []string                             // 声明请求头keys
        for k, _ := range c.Request.Header {
            headerKeys = append(headerKeys, k)
        }
        headerStr := strings.Join(headerKeys, ", ")
        if headerStr != "" {
            headerStr = fmt.Sprintf("access-control-allow-origin, access-control-allow-headers, %s", headerStr)
        } else {
            headerStr = "access-control-allow-origin, access-control-allow-headers"
        }
        if origin != "" {
            c.Writer.Header().Set("Access-Control-Allow-Origin", "*")
            c.Header("Access-Control-Allow-Origin", "*")        // 这是允许访问所有域
            c.Header("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE,UPDATE")      //服务器支持的所有跨域请求的方法,为了避免浏览次请求的多次'预检'请求
            //  header的类型
            c.Header("Access-Control-Allow-Headers", "Authorization, Content-Length, X-CSRF-Token, Token,session,X_Requested_With,Accept, Origin, Host, Connection, Accept-Encoding, Accept-Language,DNT, X-CustomHeader, Keep-Alive, User-Agent, X-Requested-With, If-Modified-Since, Cache-Control, Content-Type, Pragma")
            //              允许跨域设置                                                                                                      可以返回其他子段
            c.Header("Access-Control-Expose-Headers", "Content-Length, Access-Control-Allow-Origin, Access-Control-Allow-Headers,Cache-Control,Content-Language,Content-Type,Expires,Last-Modified,Pragma,FooBar")      // 跨域关键设置 让浏览器可以解析
            c.Header("Access-Control-Max-Age", "172800")        // 缓存请求信息 单位为秒
            c.Header("Access-Control-Allow-Credentials", "false")       //  跨域请求是否需要带cookie信息 默认设置为true
            c.Set("content-type", "application/json")       // 设置返回格式是json
        }

        //放行所有OPTIONS方法
        if method == "OPTIONS" {
            c.JSON(http.StatusOK, "Options Request!")
        }
        // 处理请求
        c.Next()        //  处理请求
    }
}

原文