Only use fmt.Errorf

handshake/handshake.go

@@ -2,7 +2,7 @@ package handshake
 
 import (
 	"bufio"
-	"errors"
+	"fmt"
 	"io"
 )
 
@@ -45,7 +45,7 @@ func Read(r *bufio.Reader) (*Handshake, error) {
 	pstrlen := int(lengthBuf[0])
 
 	if pstrlen == 0 {
-		err := errors.New("pstrlen cannot be 0")
+		err := fmt.Errorf("pstrlen cannot be 0")
 		return nil, err
 	}
 

message/message.go

@@ -3,7 +3,6 @@ package message
 import (
 	"bufio"
 	"encoding/binary"
-	"errors"
 	"fmt"
 	"io"
 )
@@ -52,7 +51,7 @@ func ParsePiece(index int, buf []byte, msg *Message) (int, error) {
 		return 0, fmt.Errorf("Expected PIECE (ID %d), got ID %d", MsgPiece, msg.ID)
 	}
 	if len(msg.Payload) < 8 {
-		return 0, errors.New("Payload too short")
+		return 0, fmt.Errorf("Payload too short. %d < 8", len(msg.Payload))
 	}
 	parsedIndex := int(binary.BigEndian.Uint32(msg.Payload[0:4]))
 	if parsedIndex != index {

torrentfile/tracker.go

@@ -2,7 +2,7 @@ package torrentfile
 
 import (
 	"encoding/binary"
-	"errors"
+	"fmt"
 	"net"
 	"net/http"
 	"net/url"
@@ -21,7 +21,7 @@ func parsePeers(peersBin string) ([]p2p.Peer, error) {
 	const peerSize = 6 // 4 for IP, 2 for port
 	numPeers := len(peersBin) / peerSize
 	if len(peersBin)%peerSize != 0 {
-		err := errors.New("Received malformed peers")
+		err := fmt.Errorf("Received malformed peers")
 		return nil, err
 	}
 	peers := make([]p2p.Peer, numPeers)