performance,typo: prealloc slice for performance and fix typo (#816)

* prealloc for performance

* mispell

consumergroup.go

@@ -326,7 +326,7 @@ type Generation struct {
 	// between Start and close.  lock protects all of them.  done is closed
 	// when the generation is ending in order to signal that the generation
 	// should start self-desructing.  closed protects against double-closing
-	// the done chan.  routines is a count of runing go routines that have been
+	// the done chan.  routines is a count of running go routines that have been
 	// launched by Start.  joined will be closed by the last go routine to exit.
 	lock     sync.Mutex
 	done     chan struct{}

createtopics.go

@@ -209,13 +209,13 @@ func (t *TopicConfig) configs() []createtopics.RequestConfig {
 }
 
 func (t TopicConfig) toCreateTopicsRequestV0Topic() createTopicsRequestV0Topic {
-	var requestV0ReplicaAssignments []createTopicsRequestV0ReplicaAssignment
+	requestV0ReplicaAssignments := make([]createTopicsRequestV0ReplicaAssignment, 0, len(t.ReplicaAssignments))
 	for _, a := range t.ReplicaAssignments {
 		requestV0ReplicaAssignments = append(
 			requestV0ReplicaAssignments,
 			a.toCreateTopicsRequestV0ReplicaAssignment())
 	}
-	var requestV0ConfigEntries []createTopicsRequestV0ConfigEntry
+	requestV0ConfigEntries := make([]createTopicsRequestV0ConfigEntry, 0, len(t.ConfigEntries))
 	for _, c := range t.ConfigEntries {
 		requestV0ConfigEntries = append(
 			requestV0ConfigEntries,
@@ -377,7 +377,7 @@ func (c *Conn) createTopics(request createTopicsRequestV0) (createTopicsResponse
 // operational semantics. In other words, if CreateTopics is invoked with a
 // configuration for an existing topic, it will have no effect.
 func (c *Conn) CreateTopics(topics ...TopicConfig) error {
-	var requestV0Topics []createTopicsRequestV0Topic
+	requestV0Topics := make([]createTopicsRequestV0Topic, 0, len(topics))
 	for _, t := range topics {
 		requestV0Topics = append(
 			requestV0Topics,

reader_test.go

@@ -1552,7 +1552,7 @@ func TestConsumerGroupWithGroupTopicsMultple(t *testing.T) {
 
 	time.Sleep(time.Second)
 
-	var msgs []Message
+	msgs := make([]Message, 0, len(conf.GroupTopics))
 	for _, topic := range conf.GroupTopics {
 		msgs = append(msgs, Message{Topic: topic})
 	}