The resource could not be loaded because the App Transport Security policy requires the use of a secure connection

I have solved it with adding some key in info.plist. The steps I followed are:

1. Opened my Project target's info.plist file

2. Added a Key called NSAppTransportSecurity as a Dictionary.

3. Added a Subkey called NSAllowsArbitraryLoads as Boolean and set its value to YES as like following image.

Clean the Project and Now Everything is Running fine as like before.

Ref Link: https://stackoverflow.com/a/32609970

EDIT: OR In source code of info.plist file we can add that:

<key>NSAppTransportSecurity</key>
    <dict>
        <key>NSAllowsArbitraryLoads</key>
        <true/>
        <key>NSExceptionDomains</key>
        <dict>
            <key>yourdomain.com</key>
            <dict>
                <key>NSIncludesSubdomains</key>
                <true/>
                <key>NSThirdPartyExceptionRequiresForwardSecrecy</key>
                <false/>
            </dict>
       </dict>
  </dict>

Be aware, using NSAllowsArbitraryLoads = true in the project's info.plist allows all connection to any server to be insecure. If you want to make sure only a specific domain is accessible through an insecure connection, try this:

Or, as source code:

<key>NSAppTransportSecurity</key>
<dict>
    <key>NSExceptionDomains</key>
    <dict>
        <key>domain.com</key>
        <dict>
            <key>NSExceptionAllowsInsecureHTTPLoads</key>
            <true/>
            <key>NSIncludesSubdomains</key>
            <true/>
        </dict>
    </dict>
</dict>

Clean & Build project after editing.

Transport security is provided in iOS 9.0 or later, and in OS X v10.11 and later.

So by default only https calls only allowed in apps. To turn off App Transport Security add following lines in info.plist file...

<key>NSAppTransportSecurity</key>
  <dict>
    <key>NSAllowsArbitraryLoads</key>
    <true/>
  </dict>

For more info:
https://developer.apple.com/library/content/documentation/General/Reference/InfoPlistKeyReference/Articles/CocoaKeys.html#//apple_ref/doc/uid/TP40009251-SW33