Completion Handler in API never runs - arrays

Question

I have an APICall as below
static func getLinkToken() {
// Prepare URL
let url = URL(string: "https://sandbox.plaid.com/link/token/create")
guard let requestUrl = url else { fatalError() }
// Prepare URL Request Object
var request = URLRequest(url: requestUrl)
request.httpMethod = "POST"
let prePostString : [String : Any] = [
"client_id" : clientID,
"secret" : secret,
"user" : ["client_user_id": uniqueID],
"client_name": "Plaid App",
"products": ["transactions"],
"country_codes": ["US"],
"language": "en",
"account_filters": [
"depository": [
"account_subtypes": ["checking"]
]
]
]
let postString = try? JSONSerialization.data(withJSONObject: prePostString)
// Set HTTP Request Body
request.httpBody = postString;
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
// Perform HTTP Request
let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
// Check for Error
if let error = error {
print("Error took place \(error)")
return
}
do {
//Parse response into a dict
let parsedData = try JSONSerialization.jsonObject(with: data!) as! [String:Any]
//Add link token to user class
User.linkToken = (parsedData["link_token"] as! String)
} catch let error as NSError {
print(error)
}
// Convert HTTP Response Data to a String
if let data = data, let dataString = String(data: data, encoding: .utf8) {
print("Response data string:\n \(dataString)")
}
}
task.resume()
}
For some reason this code never works if I call it unless it is in #main.init.
It appears that when I call the function in any class/method other than the initializer for main, the completion handler never runs. An example of how I call it is shown below.
class Practice {
func getAPI() {
getLinkToken()
}
}
TLDR; completion handler in API call never runs.
Thanks