Taskはキャンセルされても明示的にtry Task.checkCancellation()などで抜けない限り最後まで走り抜ける

main.swift

import Foundation

func mySleep(seconds: Int) async {
    await withCheckedContinuation { c in
        DispatchQueue.global().asyncAfter(deadline: .now() + TimeInterval(seconds)) {
            c.resume()
        }
    }
}

func throwingFunc() async throws {
    print(#function, "begin")
    defer {
        print(#function, "defer")
    }
    await mySleep(seconds: 2)
    print(#function, "end")
}

func nonThrowingFunc() async {
    print(#function, "begin")
    defer {
        print(#function, "defer")
    }
    await mySleep(seconds: 2)
    print(#function, "end")
}

func f1() async throws {
    await nonThrowingFunc()
    try await throwingFunc()
}

func f2() async throws {
    try await throwingFunc()
    await nonThrowingFunc()
}

try Task.checkCancellation()

print("----f1----")
let t = Task {
    try await f1()
}
sleep(1)
t.cancel()

sleep(5)
print("----f2----")
let t2 = Task {
    try await f2()
}
sleep(1)
t2.cancel()

sleep(5)
print("----end---")

stdout

----f1----
nonThrowingFunc() begin
nonThrowingFunc() end
nonThrowingFunc() defer
throwingFunc() begin
throwingFunc() end
throwingFunc() defer
----f2----
throwingFunc() begin
throwingFunc() end
throwingFunc() defer
nonThrowingFunc() begin
nonThrowingFunc() end
nonThrowingFunc() defer
----end---