How to get the return value from a thread?

The function foo below returns a string 'foo'. How can I get the value 'foo' which is returned from the thread's target?

from threading import Thread

def foo(bar):
    print('hello {}'.format(bar))
    return 'foo'
    
thread = Thread(target=foo, args=('world!',))
thread.start()
return_value = thread.join()

The "one obvious way to do it", shown above, doesn't work: thread.join() returned None.