client: drop Client.tls

This is unused.

client.go

@@ -23,10 +23,8 @@ import (
 type Client struct {
 	// keep a reference to the connection so it can be used to create a TLS
 	// connection later
-	conn net.Conn
-	text *textproto.Conn
-	// whether the Client is using TLS
-	tls        bool
+	conn       net.Conn
+	text       *textproto.Conn
 	serverName string
 	lmtp       bool
 	// map of supported extensions
@@ -138,9 +136,6 @@ func (c *Client) setConn(conn net.Conn) {
 		Closer: conn,
 	}
 	c.text = textproto.NewConn(rwc)
-
-	_, isTLS := conn.(*tls.Conn)
-	c.tls = isTLS
 }
 
 // Close closes the connection.

client_test.go

@@ -34,7 +34,6 @@ func TestClientAuthTrimSpace(t *testing.T) {
 		&wrote,
 	}
 	c := NewClient(fake)
-	c.tls = true
 	c.didHello = true
 	c.Auth(toServerEmptyAuth{})
 	c.Close()
@@ -110,8 +109,6 @@ func TestBasic(t *testing.T) {
 		t.Fatalf("Second VRFY: expected verification, got %s", err)
 	}
 
-	// fake TLS so authentication won't complain
-	c.tls = true
 	c.serverName = "smtp.google.com"
 	if err := c.Auth(sasl.NewPlainClient("", "user", "pass")); err != nil {
 		t.Fatalf("AUTH failed: %s", err)
@@ -428,7 +425,6 @@ func TestHello(t *testing.T) {
 		case 2:
 			err = c.Verify("[email protected]")
 		case 3:
-			c.tls = true
 			c.serverName = "smtp.google.com"
 			err = c.Auth(sasl.NewPlainClient("", "user", "pass"))
 		case 4:
@@ -538,7 +534,6 @@ func TestAuthFailed(t *testing.T) {
 	c := NewClient(fake)
 	defer c.Close()
 
-	c.tls = true
 	c.serverName = "smtp.google.com"
 	err := c.Auth(sasl.NewPlainClient("", "user", "pass"))