flathttp: add max duration to wait until we timeout a request

flathttp/middleware.go

@@ -1,18 +1,43 @@
 package flathttp
 
 import (
+	"context"
+	"errors"
 	"net/http"
 	"strconv"
+	"time"
 )
 
 type Middleware struct {
 	MinContentLength int64 // inclusive
 	MaxContentLength int64 // inclusive
 
+	Timeout time.Duration // max duration we are allowing a request to take
+
 	Accepts []string // content types that are accepted
 }
 
 func (m *Middleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if m.Timeout > 0 {
+		ctx, cancel := context.WithTimeout(r.Context(), m.Timeout)
+
+		defer func() {
+			cancel()
+
+			if !errors.Is(ctx.Err(), context.DeadlineExceeded) {
+				return
+			}
+
+			tmpl := `{"error": "request took too long", "max_timeout": "[[TIMEOUT]]"}`
+
+			w.Header().Set("Content-Type", "application/json")
+			w.Header().Set("X-Content-Type-Options", "nosniff")
+
+			w.WriteHeader(http.StatusGatewayTimeout)
+			w.Write(T(tmpl, F{"TIMEOUT": m.Timeout.String()}))
+		}()
+	}
+
 	if r.ContentLength <= m.MinContentLength || r.ContentLength >= m.MaxContentLength {
 		tmpl := `{"error": "content length is not acceptable", "given": [[GIVEN]], "min": [[MIN]], "max": [[MAX]]}`