Cộng đồng Go ưa chuộng cách làm web không dùng framework, chủ yếu chỉ dùng stdlib như net/http. Uư điểm này giúp web app Go bớt đi nhiều dependency, bù lại, nhiều thứ phải tự làm/low level.
Ví dụ sau đúng cho cả gorilla/mux lẫn net/http:
package main
import (
"fmt"
"html"
"log"
"net/http"
)
func main() {
http.HandleFunc("/bar", func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
})
log.Fatal(http.ListenAndServe(":8080", nil))
}
Output khi truy cập /bar:
2025/03/04 06:57:11 http: superfluous response.WriteHeader call from main.main.func1 (main.go:15)
Do dòng trên đã viết "Hello" vào response, nó đã tự set HTTP status code 200. Dòng http.Error set status code 400 nhưng không có tác dụng gì. Trong go doc ResponseWriter viết:
// WriteHeader sends an HTTP response header with the provided
// 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 or 1xx informational responses.
//
// The provided code must be a valid HTTP 1xx-5xx status code.
// Any number of 1xx headers may be written, followed by at most
// one 2xx-5xx header. 1xx headers are sent immediately, but 2xx-5xx
// headers may be buffered. Use the Flusher interface to send
// buffered data. The header map is cleared when 2xx-5xx headers are
// sent, but not with 1xx headers.
//
// The server will automatically send a 100 (Continue) header
// on the first read from the request body if the request has
// an "Expect: 100-continue" header.
hay trong Gorilla/mux viết:
Middlewares should write to ResponseWriter if they are going to terminate the request, and they should not write to ResponseWriter if they are not going to terminate it. source
Kết luận
Happy bug fixing.
Hết.
HVN at https://pymi.vn and https://www.familug.org.