# Functions
Connect connects to MQTT broker and returns a Client.
# Constants
AtLeastOnce represents "acknowledged delivery" (>=1).
AtMostOnce represents "fire and forget" (<=1).
ExactlyOnce represents "assured delivery" (=1).
Explicitly shows called Disconnect() explicitly.
Failure indicates "subscription failed".
Timeout shows by timeout.
# Variables
DefaultOptions represents default values which used for when Connect()'s opts argument is nil.
ErrTerminated indicates the operation is terminated.
ErrUnknownProtocol indicates connect adddress includes unknown protocol.
# Structs
Message represents a MQTT's published message.
Options represents connect options.
Param represents connection parameters for MQTT client.
SubscribeError is detailed error for Subscribe().
Topic represents a topic filter fanned in.
UnsubscribeError is detailed error for Unsubscribe().
Will represents MQTT's will message.
# Interfaces
Client is a MQTT client.
# Type aliases
DisconnectedFunc is called when a connection was lost.
PublishedFunc is called when receive a message.
QoS represents QoS levels of MQTT.
Reason represents reason of disconnection.