Fix mispelling

resolves eclipse-paho#123

Author: alsm

client.go

@@ -107,7 +107,7 @@ func NewClient(o *ClientOptions) Client {
 	c.status = disconnected
 	c.messageIds = messageIds{index: [65535]Token{}}
 	c.msgRouter, c.stopRouter = newRouter()
-	c.msgRouter.setDefaultHandler(c.options.DefaultPublishHander)
+	c.msgRouter.setDefaultHandler(c.options.DefaultPublishHandler)
 	if !c.options.AutoReconnect {
 		c.options.MessageChannelDepth = 0
 	}

options.go

@@ -58,7 +58,7 @@ type ClientOptions struct {
 	MaxReconnectInterval    time.Duration
 	AutoReconnect           bool
 	Store                   Store
-	DefaultPublishHander    MessageHandler
+	DefaultPublishHandler   MessageHandler
 	OnConnect               OnConnectHandler
 	OnConnectionLost        ConnectionLostHandler
 	WriteTimeout            time.Duration
@@ -235,7 +235,7 @@ func (o *ClientOptions) SetBinaryWill(topic string, payload []byte, qos byte, re
 // SetDefaultPublishHandler sets the MessageHandler that will be called when a message
 // is received that does not match any known subscriptions.
 func (o *ClientOptions) SetDefaultPublishHandler(defaultHandler MessageHandler) *ClientOptions {
-	o.DefaultPublishHander = defaultHandler
+	o.DefaultPublishHandler = defaultHandler
 	return o
 }