etcdserver: fixes shadowed variables for go tool vet

Fix for https://github.com/coreos/etcd/issues/3954.

etcdserver/cluster_util.go

@@ -78,7 +78,7 @@ func getClusterFromRemotePeers(urls []string, timeout time.Duration, logerr bool
 			continue
 		}
 		var membs []*Member
-		if err := json.Unmarshal(b, &membs); err != nil {
+		if err = json.Unmarshal(b, &membs); err != nil {
 			if logerr {
 				plog.Warningf("could not unmarshal cluster response: %v", err)
 			}
@@ -246,7 +246,7 @@ func getVersion(m *Member, rt http.RoundTripper) (*version.Versions, error) {
 			continue
 		}
 		var vers version.Versions
-		if err := json.Unmarshal(b, &vers); err != nil {
+		if err = json.Unmarshal(b, &vers); err != nil {
 			plog.Warningf("failed to unmarshal the response body got from the peerURL(%s) of member %s (%v)", u, m.ID, err)
 			continue
 		}

etcdserver/raft.go

@@ -158,14 +158,14 @@ func (r *raftNode) start(s *EtcdServer) {
 					}
 				}
 
-				apply := apply{
+				ap := apply{
 					entries:  rd.CommittedEntries,
 					snapshot: rd.Snapshot,
 					done:     make(chan struct{}),
 				}
 
 				select {
-				case r.applyc <- apply:
+				case r.applyc <- ap:
 				case <-r.stopped:
 					return
 				}
@@ -185,7 +185,7 @@ func (r *raftNode) start(s *EtcdServer) {
 				r.s.send(rd.Messages)
 
 				select {
-				case <-apply.done:
+				case <-ap.done:
 				case <-r.stopped:
 					return
 				}
@@ -253,7 +253,7 @@ func startNode(cfg *ServerConfig, cl *cluster, ids []types.ID) (id types.ID, n r
 			ClusterID: uint64(cl.ID()),
 		},
 	)
-	if err := os.MkdirAll(cfg.SnapDir(), privateDirMode); err != nil {
+	if err = os.MkdirAll(cfg.SnapDir(), privateDirMode); err != nil {
 		plog.Fatalf("create snapshot directory error: %v", err)
 	}
 	if w, err = wal.Create(cfg.WALDir(), metadata); err != nil {

etcdserver/server.go

@@ -1037,7 +1037,7 @@ func (s *EtcdServer) snapshot(snapi uint64, confState raftpb.ConfState) {
 		}
 		// SaveSnap saves the snapshot and releases the locked wal files
 		// to the snapshot index.
-		if err := s.r.storage.SaveSnap(snap); err != nil {
+		if err = s.r.storage.SaveSnap(snap); err != nil {
 			plog.Fatalf("save snapshot error: %v", err)
 		}
 		plog.Infof("saved snapshot at index %d", snap.Metadata.Index)