CustomArguments.swift

import UIKit

protocol GETProtocol {
    associatedtype GETArguments
    static func get(_ args: GETArguments)
}

protocol POSTProtocol {
    associatedtype POSTArguments
    static func post(_ args: POSTArguments)
}

struct Endpoint: GETProtocol, POSTProtocol {
    
    typealias GETArguments = Void
    static func get(_ args: Void) {
        print("get")
    }
    
    typealias POSTArguments = String
    static func post(_ args: String) {
        print("post: \(args)")
    }
    
}

Endpoint.get()        // get
Endpoint.post("hoge") // post: hoge