add ruleguard support, fix all the reported issues (#10335)

cmd/streaming-signature-v4_test.go

@@ -184,7 +184,7 @@ func TestParseHexUint(t *testing.T) {
 	for _, tt := range tests {
 		got, err := parseHexUint([]byte(tt.in))
 		if tt.wantErr != "" {
-			if !strings.Contains(fmt.Sprint(err), tt.wantErr) {
+			if err != nil && !strings.Contains(err.Error(), tt.wantErr) {
 				t.Errorf("parseHexUint(%q) = %v, %v; want error %q", tt.in, got, err, tt.wantErr)
 			}
 		} else {