问题
This answer about static to static (file:// -> file://) states that a webserver (http://) can be used to serve files to a local static page (file://) without violating CORS. And this answer states that when sending data from a webserver to a static page, a header of null must be used. But neither of the two lines below are working, so how do I do it?
func handler(w http.ResponseWriter, r *http.Request) {
w.Header().Add("Access-Control-Allow-Origin", nil) //this line
fmt.Fprintf(w, "Hi there, I love %s!", r.URL.Path[1:])
}
returns the error ./main.go:42: cannot use nil as type string in argument to w.Header().Add
func handler(w http.ResponseWriter, r *http.Request) {
w.Header().Add("Access-Control-Allow-Origin", "")
fmt.Fprintf(w, "Hi there, I love %s!", r.URL.Path[1:])
}
This compiles but throws the client side error: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8080/aardvark/posts. (Reason: CORS header 'Access-Control-Allow-Origin' missing)
回答1:
After writing up this question, I thought to try one last thing out of desperation, and it worked.
func handler(w http.ResponseWriter, r *http.Request) {
w.Header().Add("Access-Control-Allow-Origin", "null")
fmt.Fprintf(w, "Hi there, I love %s!", r.URL.Path[1:])
}
You're supposed to set the string to "null", rather than a null string "" or nil
If you don't think this question belongs on SO, please leave a comment and I'll promptly take it down.
来源：https://stackoverflow.com/questions/35966549/golang-setting-header-to-null-for-a-file-to-http-request-not-working