all: gometalinter (#843)

* kubernetes/reverse: remove deadcode
* deadcode in errors and kubernetes removed
* unnecessary conversion
* constants
* proxy: time.Since()
* simplications
* static check
* Disable test/external_test

middleware/proxy/lookup.go

@@ -97,7 +97,7 @@ func (p Proxy) lookup(state request.Request) (*dns.Msg, error) {
 
 		// Since Select() should give us "up" hosts, keep retrying
 		// hosts until timeout (or until we get a nil host).
-		for time.Now().Sub(start) < tryDuration {
+		for time.Since(start) < tryDuration {
 			host := upstream.Select()
 			if host == nil {
 				return nil, errUnreachable

middleware/proxy/proxy.go

@@ -109,7 +109,7 @@ func (p Proxy) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 
 		// Since Select() should give us "up" hosts, keep retrying
 		// hosts until timeout (or until we get a nil host).
-		for time.Now().Sub(start) < tryDuration {
+		for time.Since(start) < tryDuration {
 			host := upstream.Select()
 			if host == nil {