Test your API

testMailgunWebhook.swift

// Test Webhook
// https://app.mailgun.com/app/webhooks
// WTFPL License

import Foundation

// Postbin URL
let urlString = "http://bin.mailgun.net/d806fafc"

// Sample Parameter: signature
let mailgunSignatureDict: [String: Any] = [
    "timestamp": "1561003406",
    "token": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    "signature": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
]

extension String {
    // Convert Dictionary to JSON String
    static func convert(dict: [String: Any]) -> String? {
        do {
            let jsonData = try JSONSerialization.data(withJSONObject: dict, options: .prettyPrinted)
            let jsonText = String(data: jsonData, encoding: .ascii)
            return jsonText
        } catch {
            print(error.localizedDescription)
            return nil
        }
    }
}

// JSON String
let jsonText = String.convert(dict: mailgunSignatureDict)

var url = URLComponents(string: urlString)!
url.queryItems = [
    URLQueryItem(name: "signature", value: jsonText),
    URLQueryItem(name: "testURLQueryItem", value: "testValue")
]
var request = URLRequest(url: url.url!)
request.httpMethod = "POST"

URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print(error)
    }
    guard let data = data else {
        return
    }
    if let response = response {
        print(response)
    }
    if let json = try? JSONSerialization.jsonObject(with: data, options: []) {
        print(json)
    }
}.resume()