beego解决跨域问题：options请求、axios post请求跨域问题

根据网上的资料配置，还是未能解决跨域的问题，错误如下：

has been blocked by CORS policy: The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.

网上的配置如下：

beego.InsertFilter("/*", beego.BeforeRouter, cors.Allow(&cors.Options{
	AllowAllOrigins:  true,
	AllowMethods:     []string{"*"},
	AllowHeaders:     []string{"*"},
	AllowCredentials: true,
}))

---

正确的配置（2020-05-10 依然不能完全解决）

beego.InsertFilter("/*", beego.BeforeRouter, cors.Allow(&cors.Options{
	AllowOrigins:     []string{"*"},
	AllowMethods:     []string{"*"},
	AllowHeaders:     []string{"*"},
	AllowCredentials: true,
}))

2020-05-10：上面的配置，在碰到options请求的时候，依然还是会提示跨域问题：

Request header field Content-Type is not allowed by Access-Control-Allow-Headers in preflight response

The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.

等等报错。

解决

既然用这些配置没法解决，那就自己撸一个吧。

cors_filter.go

var success = []byte("SUPPORT OPTIONS")

var corsFunc = func(ctx *context.Context) {
	origin := ctx.Input.Header("Origin")
	ctx.Output.Header("Access-Control-Allow-Methods", "OPTIONS,DELETE,POST,GET,PUT,PATCH")
	ctx.Output.Header("Access-Control-Max-Age", "3600")
	ctx.Output.Header("Access-Control-Allow-Headers", "X-Custom-Header,accept,Content-Type,Access-Token")
	ctx.Output.Header("Access-Control-Allow-Credentials", "true")
	ctx.Output.Header("Access-Control-Allow-Origin", origin)
	if ctx.Input.Method() == http.MethodOptions {
		// options请求，返回200
		ctx.Output.SetStatus(http.StatusOK)
		_ = ctx.Output.Body(success)
	}
}

func init() {
	beego.InsertFilter("/*", beego.BeforeRouter, corsFunc)
}

加了这个配置之后，跨域总算解决了。