server: small cleanups (#2740)

Rename connTimeout to graceTimeout to be more instructive on it's use,
some whitespace for imports lines.
Signed-off-by: Miek Gieben <miek@miek.nl>

core/dnsserver/listen_go111.go

@@ -9,6 +9,7 @@ import (
 	"syscall"
 
 	"github.com/coredns/coredns/plugin/pkg/log"
+
 	"golang.org/x/sys/unix"
 )
 

core/dnsserver/server.go

@@ -35,7 +35,7 @@ type Server struct {
 
 	zones        map[string]*Config // zones keyed by their address
 	dnsWg        sync.WaitGroup     // used to wait on outstanding connections
-	connTimeout time.Duration      // the maximum duration of a graceful shutdown
+	graceTimeout time.Duration      // the maximum duration of a graceful shutdown
 	trace        trace.Trace        // the trace plugin for the server
 	debug        bool               // disable recover()
 	classChaos   bool               // allow non-INET class queries
@@ -48,7 +48,7 @@ func NewServer(addr string, group []*Config) (*Server, error) {
 	s := &Server{
 		Addr:         addr,
 		zones:        make(map[string]*Config),
-		connTimeout: 5 * time.Second, // TODO(miek): was configurable
+		graceTimeout: 5 * time.Second,
 	}
 
 	// We have to bound our wg with one increment
@@ -163,7 +163,7 @@ func (s *Server) Stop() (err error) {
 		// Wait for remaining connections to finish or
 		// force them all to close after timeout
 		select {
-		case <-time.After(s.connTimeout):
+		case <-time.After(s.graceTimeout):
 		case <-done:
 		}
 	}