Misspell correction (#826)

Did a `misspell . | grep -v ^vendor` and fixed
several typos.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

middleware/cache/freq/freq.go

@@ -7,7 +7,7 @@ import (
 	"time"
 )
 
-// Freq tracks the frequence of things.
+// Freq tracks the frequencies of things.
 type Freq struct {
 	// Last time we saw a query for this element.
 	last time.Time

middleware/cache/handler.go

@@ -43,7 +43,7 @@ func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 
 		if c.prefetch > 0 && i.Freq.Hits() > c.prefetch && pct < c.percentage {
 			// When prefetching we loose the item i, and with it the frequency
-			// that we've gathered sofar. See we copy the frequence info back
+			// that we've gathered sofar. See we copy the frequencies info back
 			// into the new item that was stored in the cache.
 			prr := &ResponseWriter{ResponseWriter: w, Cache: c, prefetch: true}
 			middleware.NextOrFailure(c.Name(), c.Next, ctx, prr, r)

middleware/dnstap/taprw/writer.go

@@ -26,7 +26,7 @@ type ResponseWriter struct {
 	err  error
 }
 
-// Check if a dnstap error occured.
+// Check if a dnstap error occurred.
 // Set during ResponseWriter.Write.
 func (w ResponseWriter) DnstapError() error {
 	return w.err

middleware/file/lookup.go

@@ -39,7 +39,7 @@ func (z *Zone) Lookup(state request.Request, qname string) ([]dns.RR, []dns.RR,
 		}
 	}()
 
-	// If z is a secondary zone we might not have transfered it, meaning we have
+	// If z is a secondary zone we might not have transferred it, meaning we have
 	// all zone context setup, except the actual record. This means (for one thing) the apex
 	// is empty and we don't have a SOA record.
 	soa := z.Apex.SOA

middleware/kubernetes/autopath.go

@@ -6,7 +6,7 @@ import "github.com/miekg/dns"
 // * reverts question section of a packet to its original state.
 //   This is done to avoid the 'Question section mismatch:' error in client.
 // * Defers write to the client if the response code is NXDOMAIN.  This is needed
-//   to enable further search path probing if a search was not sucessful.
+//   to enable further search path probing if a search was not successful.
 // * Allow forced write to client regardless of response code.  This is needed to
 //   write the packet to the client if the final search in the path fails to
 //   produce results.

middleware/kubernetes/kubernetes_test.go

@@ -71,7 +71,7 @@ func TestIsNameError(t *testing.T) {
 	if !k.IsNameError(errInvalidRequest) {
 		t.Errorf("Expected 'true' for '%v'", errInvalidRequest)
 	}
-	otherErr := errors.New("Some other error occured")
+	otherErr := errors.New("Some other error occurred")
 	if k.IsNameError(otherErr) {
 		t.Errorf("Expected 'true' for '%v'", otherErr)
 	}