matchRequest function
Implementation
TransformingPredicate<Request, Future<Pair<Map<String, String>, String>>>
matchRequest(String method, String pathExpression) {
var pattern = UriPattern(pathExpression);
return predicate(
(Request request) =>
request.method == method && pattern.matches(request.requestedUri.path),
(Request request) async =>
Pair(_extractHeaders(request, pattern), await request.readAsString()),
'$method $pathExpression',
);
}