diff --git a/bencode/iszero_go1.12.go b/bencode/iszero_go1.12.go
index 1aef6ef..8b3e144 100644
--- a/bencode/iszero_go1.12.go
+++ b/bencode/iszero_go1.12.go
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build !go1.13
 // +build !go1.13
 
 package bencode
diff --git a/bencode/iszero_go1.13.go b/bencode/iszero_go1.13.go
index 5cf744b..0aeba6a 100644
--- a/bencode/iszero_go1.13.go
+++ b/bencode/iszero_go1.13.go
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.13
 // +build go1.13
 
 package bencode
diff --git a/dht/dht_server.go b/dht/dht_server.go
index b24d398..fbc576d 100644
--- a/dht/dht_server.go
+++ b/dht/dht_server.go
@@ -317,12 +317,12 @@ func (s *Server) Node6Num() int { return s.routingTable6.Len() }
 // AddNode adds the node into the routing table.
 //
 // The returned value:
-//   NodeAdded:           The node is added successfully.
-//   NodeNotAdded:        The node is not added and is discarded.
-//   NodeExistAndUpdated: The node has existed, and its status has been updated.
-//   NodeExistAndChanged: The node has existed, but the address is inconsistent.
-//                        The current node will be discarded.
 //
+//	NodeAdded:           The node is added successfully.
+//	NodeNotAdded:        The node is not added and is discarded.
+//	NodeExistAndUpdated: The node has existed, and its status has been updated.
+//	NodeExistAndChanged: The node has existed, but the address is inconsistent.
+//	                     The current node will be discarded.
 func (s *Server) AddNode(node krpc.Node) int {
 	// For IPv6
 	if node.Addr.IsIPv6() {
diff --git a/dht/routing_table.go b/dht/routing_table.go
index ce68c1a..6d8b95d 100644
--- a/dht/routing_table.go
+++ b/dht/routing_table.go
@@ -155,12 +155,12 @@ func (rt *routingTable) Stop() {
 // AddNode adds the node into the routing table.
 //
 // The returned value:
-//   NodeAdded:           The node is added successfully.
-//   NodeNotAdded:        The node is not added and is discarded.
-//   NodeExistAndUpdated: The node has existed, and its status has been updated.
-//   NodeExistAndChanged: The node has existed, but the address is inconsistent.
-//                        The current node will be discarded.
 //
+//	NodeAdded:           The node is added successfully.
+//	NodeNotAdded:        The node is not added and is discarded.
+//	NodeExistAndUpdated: The node has existed, and its status has been updated.
+//	NodeExistAndChanged: The node has existed, but the address is inconsistent.
+//	                     The current node will be discarded.
 func (rt *routingTable) AddNode(n krpc.Node) (r int) {
 	if n.ID == rt.root { // Don't add itself.
 		return NodeNotAdded
diff --git a/blockhandler/block_download_handler.go b/downloadhandler/block_download_handler.go
similarity index 100%
rename from blockhandler/block_download_handler.go
rename to downloadhandler/block_download_handler.go
diff --git a/metainfo/address.go b/metainfo/address.go
index 3c52e17..1931f7d 100644
--- a/metainfo/address.go
+++ b/metainfo/address.go
@@ -270,7 +270,8 @@ func (a Address) String() string {
 }
 
 // Equal reports whether n is equal to o, which is equal to
-//   n.HasIPAndPort(o.IP, o.Port)
+//
+//	n.HasIPAndPort(o.IP, o.Port)
 func (a Address) Equal(o Address) bool {
 	return a.Port == o.Port && a.IP.String() == o.IP.String()
 }
diff --git a/peerprotocol/fastset.go b/peerprotocol/fastset.go
index 05f7b28..150fdd3 100644
--- a/peerprotocol/fastset.go
+++ b/peerprotocol/fastset.go
@@ -25,10 +25,11 @@ import (
 // GenerateAllowedFastSet generates some allowed fast set of the torrent file.
 //
 // Argument:
-//   set: generated piece set, the length of which is the number to be generated.
-//   sz: the number of pieces in torrent.
-//   ip: the of the remote peer of the connection.
-//   infohash: infohash of torrent.
+//
+//	set: generated piece set, the length of which is the number to be generated.
+//	sz: the number of pieces in torrent.
+//	ip: the of the remote peer of the connection.
+//	infohash: infohash of torrent.
 //
 // BEP 6
 func GenerateAllowedFastSet(set []uint32, sz uint32, ip net.IP, infohash metainfo.Hash) {
diff --git a/blockhandler/block_upload_handler.go b/uploadhandler/block_upload_handler.go
similarity index 94%
rename from blockhandler/block_upload_handler.go
rename to uploadhandler/block_upload_handler.go
index afce147..3fc9522 100644
--- a/blockhandler/block_upload_handler.go
+++ b/uploadhandler/block_upload_handler.go
@@ -31,9 +31,7 @@ type BlockUploadHandler struct {
 }
 
 // NewBlockUploadHandler returns a new BlockUploadHandler.
-func NewBlockUploadHandler(info metainfo.Info,
-	onBlock func(pieceIndex, pieceOffset uint32, b []byte) error,
-	respondBlock func(c *pp.PeerConn) error) BlockUploadHandler {
+func NewBlockUploadHandler(info metainfo.Info, onBlock func(pieceIndex, pieceOffset uint32, b []byte) error, respondBlock func(c *pp.PeerConn) error) BlockUploadHandler {
 	return BlockUploadHandler{
 		Info:         info,
 		OnBlock:      onBlock,