golangci(lint) : more linters (#2870)

recovery.go

@@ -6,6 +6,7 @@ package gin
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -60,7 +61,8 @@ func CustomRecoveryWithWriter(out io.Writer, handle RecoveryFunc) HandlerFunc {
 				// condition that warrants a panic stack trace.
 				var brokenPipe bool
 				if ne, ok := err.(*net.OpError); ok {
-					if se, ok := ne.Err.(*os.SyscallError); ok {
+					var se *os.SyscallError
+					if errors.As(ne, &se) {
 						if strings.Contains(strings.ToLower(se.Error()), "broken pipe") || strings.Contains(strings.ToLower(se.Error()), "connection reset by peer") {
 							brokenPipe = true
 						}