问题内容
每当我尝试从 Angular 应用程序向 Go 服务器发送 HTTP 请求时，我都会收到以下响应：
对预检请求的响应未通过访问控制检查：请求的资源上不存在“Access-Control-Allow-Origin”标头。
我添加了错误响应中详细说明的标头，但错误仍然存在。
服务器.go
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package rest
import (
"context"
"fmt"
"net/http"
"os"
"os/signal"
"sync"
"syscall"
"github.com/gorilla/mux"
"github.com/randyVerduguez/randy-verduguez_06122023-BE-challenge/configs"
"github.com/randyVerduguez/randy-verduguez_06122023-BE-challenge/http/rest/handlers"
"github.com/randyVerduguez/randy-verduguez_06122023-BE-challenge/pkg/db"
"github.com/rs/cors"
"github.com/sirupsen/logrus"
)
type Server struct {
logger *logrus.Logger
router *mux.Router
config configs.Config
}
func NewServer() (*Server, error) {
config, err := configs.NewParsedConfig()
if err != nil {
return nil, err
}
database, err := db.Connect(db.ConfigDB{
Host: config.Database.Host,
Port: config.Database.Port,
User: config.Database.User,
Password: config.Database.Password,
Name: config.Database.Name,
})
if err != nil {
return nil, err
}
log, err := NewLogger()
if err != nil {
return nil, err
}
router := mux.NewRouter()
handlers.Register(router, log, database)
server := Server{
logger: log,
config: config,
router: router,
}
return &server, nil
}
func (s *Server) Run(ctx context.Context) error {
cors := cors.New(cors.Options{
AllowedMethods: []string{"GET, POST"},
AllowedOrigins: []string{"http://localhost:4200"},
AllowedHeaders: []string{"Content-Type", "Accept"},
})
server := http.Server{
Addr: fmt.Sprintf(":%d", s.config.ServerPort),
Handler: cors.Handler(s.router),
}
stopServer := make(chan os.Signal, 1)
signal.Notify(stopServer, syscall.SIGINT, syscall.SIGTERM)
defer signal.Stop(stopServer)
serverErrors := make(chan error, 1)
var wg sync.WaitGroup
wg.Add(1)
go func(wg *sync.WaitGroup) {
defer wg.Done()
s.logger.Printf("REST API listening on %d", s.config.ServerPort)
serverErrors <- server.ListenAndServe()
}(&wg)
select {
case err := <-serverErrors:
return fmt.Errorf("error: starting REST API server %w", err)
case <-stopServer:
s.logger.Warn("server recieved STOP signal")
err := server.Shutdown(ctx)
if err != nil {
return fmt.Errorf("graceful shutdown did not complete: %w", err)
}
wg.Wait()
s.logger.Info("server was shutdown gracefully")
}
return nil
}
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Access-Control-Allow-Origin", "http://localhost:4200")
w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS")
w.Header().Set("Access-Control-Allow-Credentials", "true")
w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization, Accept, origin, Cache-Control, X-Requested-With")
if r.Method == "OPTIONS" {
return
}
s.router.ServeHTTP(w, r)
}
路线.go
package handlers
import (
"net/http"
"github.com/gorilla/mux"
"github.com/jmoiron/sqlx"
"github.com/sirupsen/logrus"
)
func Register(r *mux.Router, lg *logrus.Logger, db *sqlx.DB) {
handler := newHandler(lg, db)
r.Use(handler.MiddlewareLogger())
r.HandleFunc("/weather/current", handler.GetCurrentWeather()).Methods(http.MethodPost)
r.HandleFunc("/weather/welcome", handler.Test()).Methods(http.MethodGet)
}正确答案
我注意到的第一个问题是：
AllowedMethods: []string{"GET, POST"},
这应该是：
AllowedMethods: []string{"GET", "POST"}, (或者稍微不易出错的 []string{http.MethodGet, http.MethodPost})
根据文档，这是默认值（所以你可以省略它） ：
我的下一个问题是“起源是什么”； CORS 是“跨源资源共享”，旨在 “防止从一个源运行的客户端 Web 应用程序获取从另一源检索的数据”，因此了解发出请求的页面的源非常重要。您允许 http://localhost:4200 (AllowedOrigins: []string{"http://localhost:4200"}) 所以我假设您有两个服务器在本地主机上运行（但如果这不是案件）。如果您希望允许所有来源，请使用 "*";为了进行测试，我将使用 test-cors.org - 只需转到该网站，输入 URL，例如“http://127.0.0.1:8080/weather/welcome”，进入“远程URL”，点击“发送请求”进行测试。
您的代码有点令人困惑（例如 http://localhost:4200 未使用 - 请旨在提供 最小，可重现的示例，当在这里提问时），所以我稍微简化了一些事情，希望以下内容能为您指明正确的方向。
package main
import (
"context"
"fmt"
"net/http"
"github.com/gorilla/mux"
"github.com/rs/cors"
)
func main() {
s, err := NewServer()
if err != nil {
panic(err)
}
s.Run(context.Background())
}
type Server struct {
router *mux.Router
}
func NewServer() (*Server, error) {
router := mux.NewRouter()
Register(router)
server := Server{
router: router,
}
return &server, nil
}
func (s *Server) Run(ctx context.Context) {
cors := cors.New(cors.Options{
AllowedMethods: []string{http.MethodGet, http.MethodPost},
AllowedOrigins: []string{"https://www.php.cn/link/9113c52c5f26af1782e6bf7c56973ef4"},
// AllowedOrigins: []string{"*"},
AllowedHeaders: []string{"Content-Type", "Accept"},
})
server := http.Server{
Addr: fmt.Sprintf(":%d", 8080),
Handler: cors.Handler(s.router),
}
fmt.Println(server.ListenAndServe())
}
type handler struct{}
func Register(r *mux.Router) {
handler := handler{}
r.HandleFunc("/", handler.Index).Methods(http.MethodGet)
r.HandleFunc("/weather/welcome", handler.Test).Methods(http.MethodGet)
}
// Index - Provide a simple page with a link to the other page to simplify testing
func (h *handler) Index(w http.ResponseWriter, _ *http.Request) {
w.Write([]byte(`Test Link`))
}
// The real page
func (h *handler) Test(w http.ResponseWriter, _ *http.Request) {
fmt.Println("Test Called")
w.Write([]byte("all OK"))
} 
