Google Cloud函数不会返回我使用Go设置的CORS头

Question

func HelloWorld(w http.ResponseWriter, r *http.Request) {
    [...]
    response := make(map[string]interface{})
    w.WriteHeader(http.StatusOK)
    w.Header().Set("Content-Type", "application/json")
    w.Header().Set("Access-Control-Allow-Origin", "*")
    w.Header().Set("Allow", "GET, OPTIONS")
    w.Header().Set("Access-Control-Allow-Methods", "GET, OPTIONS")
    w.Header().Set("Access-Control-Allow-Headers", "*")
    response["list"] = list
    if err = json.NewEncoder(w).Encode(response); err != nil {
        fmt.Println(err)
    }
}

当我尝试curl-v“https://us-central1-my-function.cloudfunctions.net/myfunction”时，我得到以下响应：

[...]
* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
* old SSL session ID is stale, removing
* Connection state changed (MAX_CONCURRENT_STREAMS == 100)!
< HTTP/2 200 
< content-type: text/plain; charset=utf-8
< function-execution-id: ivz4zonw37d1
< x-cloud-trace-context: b6929d3ddf88dc102f6f1f069404aeaa;o=1
< date: Wed, 25 Mar 2020 20:00:52 GMT
< server: Google Frontend
[...]

当我尝试从本地vuejs应用程序调用云函数时，我会得到以下错误:交叉起源请求被阻塞：同一起源策略不允许读取https://us-central1-my-function.cloudfunctions.net/myfunction的远程资源。（原因：CORS标头“Access-Control-Allow-Origin”丢失）。

Answer 1

这是你的云功能应该具备的标准形态。它应该检查preflight请求发送的OPTIONS方法并设置Heathers。那么它应该为主请求发送heathers。

在这里你可以找到更多信息：

HTTP功能

// Package http provides a set of HTTP Cloud Functions samples.
package http

import (
        "fmt"
        "net/http"
)

// CORSEnabledFunction is an example of setting CORS headers.
// For more information about CORS and CORS preflight requests, see
// https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request.
func CORSEnabledFunction(w http.ResponseWriter, r *http.Request) {
        // Set CORS headers for the preflight request
        if r.Method == http.MethodOptions {
                w.Header().Set("Access-Control-Allow-Origin", "*")
                w.Header().Set("Access-Control-Allow-Methods", "POST")
                w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
                w.Header().Set("Access-Control-Max-Age", "3600")
                w.WriteHeader(http.StatusNoContent)
                return
        }
        // Set CORS headers for the main request.
        w.Header().Set("Access-Control-Allow-Origin", "*")
        fmt.Fprint(w, "Hello, World!")
}