diff --git a/auth/center.go b/auth/center.go
index fc629a8..3579776 100644
--- a/auth/center.go
+++ b/auth/center.go
@@ -26,7 +26,7 @@ import (
 	"go.uber.org/zap"
 )
 
-const authorizationFieldPattern = `AWS4-HMAC-SHA256 Credential=(?P<access_key_id>[^/]+)/(?P<date>[^/]+)/(?P<region>[^/]*)/(?P<service>[^/]+)/aws4_request, SignedHeaders=(?P<signed_header_fields>.*), Signature=(?P<v4_signature>.*)`
+var authorizationFieldRegexp = regexp.MustCompile(`AWS4-HMAC-SHA256 Credential=(?P<access_key_id>[^/]+)/(?P<date>[^/]+)/(?P<region>[^/]*)/(?P<service>[^/]+)/aws4_request, SignedHeaders=(?P<signed_header_fields>.*), Signature=(?P<v4_signature>.*)`)
 
 const emptyStringSHA256 = `e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855`
 
@@ -54,7 +54,7 @@ func NewCenter(log *zap.Logger) *Center {
 	zstdDecoder, _ := zstd.NewReader(nil)
 	return &Center{
 		log:         log,
-		submatcher:  &regexpSubmatcher{re: regexp.MustCompile(authorizationFieldPattern)},
+		submatcher:  &regexpSubmatcher{re: authorizationFieldRegexp},
 		zstdEncoder: zstdEncoder,
 		zstdDecoder: zstdDecoder,
 	}