Attempting POST request in Swift 4 gives "TIC SSL Trust Error" - swift

Question

Configuration: developing a macOS application, macOS High Sierra 10.13.1, and Xcode version 9.1 (9B55).
Alright, I've looked all over the place for a possible solution, tried several things, and nothing's worked so far.
I have a Web service running under Spring Boot, so it uses Apache Tomcat underneath and I've configured it to use the last stable release of Java 8 (1.8u152).
Because I configured my service to use HTTPS, I created a self-signed certificate. I've read that Swift doesn't really like this, but there are things you are supposed to be able to do to mitigate that until your app is ready for production.
So I created my certificate using keytool, tested it in the browser, got the usual "Your connection is not private" warning, which I expected since it was self-signed. But after allowing the exception, it works and all HTTP requests redirect to HTTPS like I programmed it to.
Now, when I try to make a POST request in Swift, I get this group of errors:
2017-11-27 22:15:35.963123-0500 MyApp[2885:4510057] TIC SSL Trust Error [1:0x600000168c40]: 3:0
2017-11-27 22:15:35.971297-0500 MyApp[2885:4510057] NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9813)
2017-11-27 22:15:35.971344-0500 MyApp[2885:4510057] Task <1ADE665F-B044-4678-8291-BF63E579CCDE>.<1> HTTP load failed (error code: -1202 [3:-9813])
2017-11-27 22:15:35.971456-0500 MyApp[2885:4510056] Task <1ADE665F-B044-4678-8291-BF63E579CCDE>.<1> finished with error - code: -1202
Upon researching this further, I made the following additions to my Info.plist file:
<key>NSAppTransportSecurity</key>
<dict>
<key>NSExceptionDomains</key>
<dict>
<key>localhost</key>
<dict>
<key>NSExceptionAllowsInsecureHTTPLoads</key>
<true/>
<key>NSIncludesSubdomains</key>
<true/>
</dict>
</dict>
<key>NSAllowsArbitraryLoads</key>
<true/>
</dict>
I tried doing this in raw source code and via the plist editor. No luck either way.
Here is the code that attempts the POST request:
let url = Constants.SERVICE_URL + "account/post"
let body: [String : Any] =
["firstName": txtFirstName.stringValue,
"lastName": txtLastName.stringValue,
"email": txtEmail.stringValue,
"password": txtPassword.stringValue];
let req = Request.create(urlExtension: url, httpVerb: Constants.HTTP_POST, jsonBody: body)
let task = URLSession.shared.dataTask(with: req) { data, response, err in
guard let data = data, err == nil else {
reply(false)
return
}
do {
let resp = try JSONSerialization.jsonObject(with: data)
reply(resp)
} catch {
print("Error: " + error.localizedDescription)
reply(false)
}
}
task.resume()
I'm at a loss now... does anyone know what to do about this?

Answer 1

I fixed it! Since my certificate was self-signed, my Mac did not trust it by default (which makes sense). I followed the instructions at macOS Sierra: If your certificate isn’t being accepted and it worked.
Make sure to add the certificate to the System keychain.