试试看：

import Combine
import PlaygroundSupport
import UIKit

public func example(of: String, execute: () -> Void) {
    print("------ \(of) ------")
    execute()
}

var cancellable: Cancellable?

example(of: "URLSession+Publisher") {
    guard let url = URL(string: "https://jsonplaceholder.typicode.com/todos/1") else { return }

    cancellable = URLSession.shared
        .dataTaskPublisher(for: url)
        .sink(receiveCompletion: { completion in
            if case .failure(let error) = completion {
                print("Failed with error \(error)")
            } else {
                print("Success")
            }
        }, receiveValue: { data, response in
            print("Data retrieved with size \(data.count), response = \(response)")
        })
}

PlaygroundPage.current.needsIndefiniteExecution = true

您需要告诉playground页面在最后一行代码之后继续运行，以便它可以等待服务器响应，并且您需要存储可取消的代码。