chore: fix linter errors

.golangci.yml

@@ -4,16 +4,13 @@ linters-settings:
 
 linters:
   enable:
-    - deadcode
+    - unused
     - errcheck
     - gosimple
     - govet
     - ineffassign
     - staticcheck
-    - structcheck
     - typecheck
-    - unused
-    - varcheck
     - nakedret
     - gofmt
     - rowserrcheck

recovery.go

@@ -7,9 +7,9 @@ package flamego
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
 	"log"
 	"net/http"
+	"os"
 	"runtime"
 
 	"github.com/flamego/flamego/inject"
@@ -109,7 +109,7 @@ pre {
 			// Print this much at least.  If we can't find the source, it won't show.
 			_, _ = fmt.Fprintf(buf, "%s:%d (0x%x)\n", file, line, pc)
 			if file != lastFile {
-				data, err := ioutil.ReadFile(file)
+				data, err := os.ReadFile(file)
 				if err != nil {
 					continue
 				}

router.go

@@ -145,11 +145,12 @@ type Route struct {
 // addition to the request path.
 //
 // For example:
-//  f.Get("/", ...).Headers(
-//      "User-Agent", "Chrome",   // Loose match
-//      "Host", "^flamego\.dev$", // Exact match
-//      "Cache-Control", "",      // As long as "Cache-Control" is not empty
-//  )
+//
+//	f.Get("/", ...).Headers(
+//	    "User-Agent", "Chrome",   // Loose match
+//	    "Host", "^flamego\.dev$", // Exact match
+//	    "Cache-Control", "",      // As long as "Cache-Control" is not empty
+//	)
 //
 // Subsequent calls to Headers() replace previously set matches.
 func (r *Route) Headers(pairs ...string) *Route {