Exponential takes a duration and returns another one that is twice as long, +/- 50%.

NewDefaultManager is a helper constructor, suitable for most normal use in real (non-test) code.

NewManager returns a connection manager using the passed Dialer, network, and address.

ErrConnectionUnavailable is returned by the Manager's Write method when the manager cannot yield a good connection.

Manager manages a net.Conn.

AfterFunc imitates time.After.

Dialer imitates net.Dial.