Add test case for "70000000000000000" and fix

go/hexadecimal/hexadecimal.go

@@ -45,7 +45,7 @@ func convertNumStringBase(in string, base int64) (int64, error) {
 		}
 		n += a
 
-		if n < 0 {
+		if n <= 0 && in[0] != '0' {
 			return 0, errors.New("range")
 		}
 	}

go/hexadecimal/hexadecimal_test.go

@@ -30,6 +30,7 @@ var testCases = []struct {
 	{"2cg134", 0, "syntax"},
 	{"8000000000000000", 0, "range"},
 	{"9223372036854775809", 0, "range"},
+	{"70000000000000000", 0, "range"},
 }
 
 func TestParseHex(t *testing.T) {