diff --git a/asciiconverter.go b/asciiconverter.go
index ec5d0cb7..308c694c 100644
--- a/asciiconverter.go
+++ b/asciiconverter.go
@@ -37,7 +37,7 @@ func (c *asciiConverter) Read(p []byte) (n int, err error) {
 	} else {
 		data, _, err = c.reader.ReadLine()
 		if err != nil {
-			return
+			return -1, err
 		}
 	}
 
@@ -64,7 +64,7 @@ func (c *asciiConverter) Read(p []byte) (n int, err error) {
 	// client transfers it in ASCII mode
 	err = c.reader.UnreadByte()
 	if err != nil {
-		return
+		return -1, err
 	}
 
 	lastByte, err := c.reader.ReadByte()
diff --git a/client_handler.go b/client_handler.go
index ddf8f248..18f22e12 100644
--- a/client_handler.go
+++ b/client_handler.go
@@ -574,7 +574,7 @@ func (c *clientHandler) writeLine(line string) {
 		c.logger.Debug("Sending answer", "line", line)
 	}
 
-	if _, err := c.writer.WriteString(fmt.Sprintf("%s\r\n", line)); err != nil {
+	if _, err := fmt.Fprintf(c.writer, "%s\r\n", line); err != nil {
 		c.logger.Warn(
 			"Answer couldn't be sent",
 			"line", line,
diff --git a/client_handler_test.go b/client_handler_test.go
index fce99cc2..4fb26681 100644
--- a/client_handler_test.go
+++ b/client_handler_test.go
@@ -239,6 +239,7 @@ func TestClientContextConcurrency(t *testing.T) {
 		for counter < 100 {
 			_, err := c.Getwd()
 			assert.NoError(t, err)
+
 			counter++
 		}
 
@@ -350,11 +351,11 @@ type testNetConn struct {
 	remoteAddr net.Addr
 }
 
-func (*testNetConn) Read(b []byte) (n int, err error) {
+func (*testNetConn) Read(_ []byte) (n int, err error) {
 	return
 }
 
-func (*testNetConn) Write(b []byte) (n int, err error) {
+func (*testNetConn) Write(_ []byte) (n int, err error) {
 	return
 }
 
@@ -370,15 +371,15 @@ func (c *testNetConn) RemoteAddr() net.Addr {
 	return c.remoteAddr
 }
 
-func (*testNetConn) SetDeadline(t time.Time) error {
+func (*testNetConn) SetDeadline(_ time.Time) error {
 	return nil
 }
 
-func (*testNetConn) SetReadDeadline(t time.Time) error {
+func (*testNetConn) SetReadDeadline(_ time.Time) error {
 	return nil
 }
 
-func (*testNetConn) SetWriteDeadline(t time.Time) error {
+func (*testNetConn) SetWriteDeadline(_ time.Time) error {
 	return nil
 }
 
diff --git a/control_unix.go b/control_unix.go
index 752a2973..6ab45323 100644
--- a/control_unix.go
+++ b/control_unix.go
@@ -10,7 +10,7 @@ import (
 )
 
 // Control defines the function to use as dialer Control to reuse the same port/address
-func Control(network, address string, c syscall.RawConn) error {
+func Control(_, _ string, c syscall.RawConn) error {
 	var errSetOpts error
 
 	err := c.Control(func(fd uintptr) {
diff --git a/driver_test.go b/driver_test.go
index 42023956..ddcbed30 100644
--- a/driver_test.go
+++ b/driver_test.go
@@ -60,6 +60,7 @@ func NewTestServerWithDriver(t *testing.T, driver *TestServerDriver) *FtpServer
 		if err := os.MkdirAll(dir, 0750); err != nil {
 			panic(err)
 		}
+
 		driver.fs = afero.NewBasePathFs(afero.NewOsFs(), dir)
 	}
 
@@ -342,12 +343,12 @@ func (driver *TestServerDriver) GetTLSConfig() (*tls.Config, error) {
 	return nil, errNoTLS
 }
 
-func (driver *TestServerDriver) PreAuthUser(cc ClientContext, user string) error {
+func (driver *TestServerDriver) PreAuthUser(cc ClientContext, _ string) error {
 	return cc.SetTLSRequirement(driver.TLSRequirement)
 }
 
-func (driver *TestServerDriver) VerifyConnection(cc ClientContext, user string,
-	tlsConn *tls.Conn) (ClientDriver, error) {
+func (driver *TestServerDriver) VerifyConnection(_ ClientContext, _ string,
+	_ *tls.Conn) (ClientDriver, error) {
 	switch driver.TLSVerificationReply {
 	case tlsVerificationFailed:
 		return nil, errInvalidTLSCertificate
diff --git a/handle_auth.go b/handle_auth.go
index ef5831e6..bcb4d3d5 100644
--- a/handle_auth.go
+++ b/handle_auth.go
@@ -76,7 +76,7 @@ func (c *clientHandler) handlePASS(param string) error {
 
 		c.writeMessage(StatusNotLoggedIn, msg)
 		c.disconnect()
-	case err == nil:
+	default: // err == nil && c.driver != nil
 		if msg == "" {
 			msg = "Password ok, continue"
 		}
diff --git a/handle_dirs.go b/handle_dirs.go
index 361e0ef0..a832f457 100644
--- a/handle_dirs.go
+++ b/handle_dirs.go
@@ -140,7 +140,7 @@ func (c *clientHandler) handleRMDIR(params string) {
 	}
 }
 
-func (c *clientHandler) handleCDUP(param string) error {
+func (c *clientHandler) handleCDUP(_ string) error {
 	parent, _ := path.Split(c.Path())
 	if parent != "/" && strings.HasSuffix(parent, "/") {
 		parent = parent[0 : len(parent)-1]
@@ -156,7 +156,7 @@ func (c *clientHandler) handleCDUP(param string) error {
 	return nil
 }
 
-func (c *clientHandler) handlePWD(param string) error {
+func (c *clientHandler) handlePWD(_ string) error {
 	c.writeMessage(StatusPathCreated, fmt.Sprintf(`"%s" is the current directory`, quoteDoubling(c.Path())))
 
 	return nil
diff --git a/handle_files.go b/handle_files.go
index 870f984d..c371d592 100644
--- a/handle_files.go
+++ b/handle_files.go
@@ -154,6 +154,7 @@ func (c *clientHandler) doFileTransfer(tr net.Conn, file io.ReadWriter, write bo
 			"Stream copy finished",
 			"writtenBytes", written,
 		)
+
 		if written == 0 {
 			_, err = out.Write([]byte{})
 		}
@@ -293,6 +294,7 @@ func (c *clientHandler) handleCHOWN(params string) {
 	{
 		usergroup := strings.Split(spl[0], ":")
 		userName := usergroup[0]
+
 		if id, err := strconv.ParseInt(userName, 10, 32); err == nil {
 			userID = int(id)
 		} else {
@@ -432,6 +434,7 @@ func (c *clientHandler) handleSTATFile(param string) error {
 
 					return nil
 				}
+
 				files, errList = directory.Readdir(-1)
 				c.closeDirectory(directoryPath, directory)
 			}
diff --git a/handle_misc.go b/handle_misc.go
index db4bbf94..ffb8ae6e 100644
--- a/handle_misc.go
+++ b/handle_misc.go
@@ -33,13 +33,13 @@ func (c *clientHandler) handlePROT(param string) error {
 	return nil
 }
 
-func (c *clientHandler) handlePBSZ(param string) error {
+func (c *clientHandler) handlePBSZ(_ string) error {
 	c.writeMessage(StatusOK, "Whatever")
 
 	return nil
 }
 
-func (c *clientHandler) handleSYST(param string) error {
+func (c *clientHandler) handleSYST(_ string) error {
 	if c.server.settings.DisableSYST {
 		c.writeMessage(StatusCommandNotImplemented, "SYST is disabled")
 
@@ -177,7 +177,7 @@ func (c *clientHandler) handleOPTS(param string) error {
 	return nil
 }
 
-func (c *clientHandler) handleNOOP(param string) error {
+func (c *clientHandler) handleNOOP(_ string) error {
 	c.writeMessage(StatusOK, "OK")
 
 	return nil
@@ -190,7 +190,7 @@ func (c *clientHandler) handleCLNT(param string) error {
 	return nil
 }
 
-func (c *clientHandler) handleFEAT(param string) error {
+func (c *clientHandler) handleFEAT(_ string) error {
 	c.writeLine(fmt.Sprintf("%d- These are my features", StatusSystemStatus))
 	defer c.writeMessage(StatusSystemStatus, "end")
 
@@ -272,7 +272,7 @@ func (c *clientHandler) handleTYPE(param string) error {
 	return nil
 }
 
-func (c *clientHandler) handleQUIT(param string) error {
+func (c *clientHandler) handleQUIT(_ string) error {
 	c.transferWg.Wait()
 
 	var msg string
diff --git a/server.go b/server.go
index 3897041d..7180ab96 100644
--- a/server.go
+++ b/server.go
@@ -174,6 +174,7 @@ func (server *FtpServer) Listen() error {
 
 			return err
 		}
+
 		if server.settings.TLSRequired == ImplicitEncryption {
 			// implicit TLS
 			var tlsConfig *tls.Config
@@ -184,6 +185,7 @@ func (server *FtpServer) Listen() error {
 
 				return err
 			}
+
 			server.listener = tls.NewListener(server.listener, tlsConfig)
 		}
 	}
diff --git a/transfer_pasv.go b/transfer_pasv.go
index a7e58521..76253103 100644
--- a/transfer_pasv.go
+++ b/transfer_pasv.go
@@ -116,7 +116,7 @@ func (c *clientHandler) findListenerWithinPortRange(portRange *PortRange) (*net.
 	return nil, ErrNoAvailableListeningPort
 }
 
-func (c *clientHandler) handlePASV(param string) error {
+func (c *clientHandler) handlePASV(_ string) error {
 	command := c.GetLastCommand()
 	addr, _ := net.ResolveTCPAddr("tcp", ":0")
 	var tcpListener *net.TCPListener
diff --git a/transfer_test.go b/transfer_test.go
index e6103203..f556361b 100644
--- a/transfer_test.go
+++ b/transfer_test.go
@@ -91,6 +91,7 @@ func ftpUpload(t *testing.T, ftp *goftp.Client, file io.ReadSeeker, filename str
 		if strings.HasSuffix(stats.Name(), filename) {
 			found = true
 		}
+
 		if !found {
 			t.Fatal("STAT: Couldn't find file !")
 		}
@@ -959,7 +960,7 @@ func TestPASVPublicIPResolver(t *testing.T) {
 	require.NoError(t, err, "Couldn't open raw connection")
 
 	s.settings.PublicHost = ""
-	s.settings.PublicIPResolver = func(cc ClientContext) (string, error) {
+	s.settings.PublicIPResolver = func(_ ClientContext) (string, error) {
 		return "127.0.0", nil
 	}
 	// we crash if the PublicIPResolver returns an invalid IP, this must be fixed outside the lib
@@ -968,7 +969,7 @@ func TestPASVPublicIPResolver(t *testing.T) {
 	require.Equal(t, StatusServiceNotAvailable, rc)
 	require.Contains(t, resp, "invalid passive IP")
 
-	s.settings.PublicIPResolver = func(cc ClientContext) (string, error) {
+	s.settings.PublicIPResolver = func(_ ClientContext) (string, error) {
 		return "", errConnectionNotAllowed
 	}