How to set HTTP status code on http.ResponseWriter

How do I set the HTTP status code on an http.ResponseWriter (e.g. to 500 or 403)?

I can see that requests normally have a status code of 200 attached to them.

Use http.ResponseWriter.WriteHeader. From the documentation:

> WriteHeader sends an HTTP response header with status code. If WriteHeader is not called explicitly, the first call to Write will trigger an implicit WriteHeader(http.StatusOK). Thus explicit calls to WriteHeader are mainly used to send error codes.

Example:

func ServeHTTP(w http.ResponseWriter, r *http.Request) {
    w.WriteHeader(http.StatusInternalServerError)
    w.Write([]byte("500 - Something bad happened!"))
}

Apart from WriteHeader(int) you can use the helper method http.Error, for example:

func yourFuncHandler(w http.ResponseWriter, r *http.Request) {

    http.Error(w, "my own error message", http.StatusForbidden)
    
    // or using the default message error
    
    http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
}

http.Error() and http.StatusText() methods are your friends

w.WriteHeader(http.StatusInternalServerError)
w.WriteHeader(http.StatusForbidden)

full list here