How to map enum and lambda function(or function pointer)?

Here's the situation, I want to map Method enum and lambda function to make a simple web server, but I'm stuck now.

I can't find a way to map enum and lambda funciton, can anyone give an example?

Also I tried to use function pointer, but I got segmentation fault, so what's the correct way to do this trick?

Need your help, any help would be great appreciated.

method.cpp

enum class Method {
    Delete = 0,
    Get,
    Head,
    Post,
    Put,
    Connect,
    Options,
    Trace,
    Patch,
    Purge,
    InternalMethodCount,
};

struct EnumClassHash
{
    template <typename T>
    std::size_t operator()(T t) const
    {
        return static_cast<std::size_t>(t);
    }
};

dispatcher.cpp

// typedef void (*request_handler)(const Request &, Response &);
typedef void (*request_handler)(const Request &, Response &);

typedef Match self_type;

self_type &get(request_handler handler) {
    _handlers.insert(std::make_pair(Method::Get, handler));
    return *this;
}

std::unordered_map<Method, request_handler, EnumClassHash> _handlers;

main.cpp

simple_handler.crud_match(std::string("/ok"))
    .get([&](const Request &request,Response &response){
        response.body = request.url;
    });