fix panic: send on closed channel

on windows: if the term is resized when ReadString is being called and no one is reading form ws, we get a panic: send on closed channel.
It could make sense to poll getconsolescreenbufferinfo calls instead of this:
something started from the sigwinch() func

on unix: same story, sigwinch was listened upon by default but if the
signals (chan sends) were not handled, this could cause a crash

fix #7434

go.mod

@@ -68,7 +68,7 @@ require (
 	github.com/masterzen/azure-sdk-for-go v0.0.0-20161014135628-ee4f0065d00c // indirect
 	github.com/masterzen/simplexml v0.0.0-20190410153822-31eea3082786 // indirect
 	github.com/masterzen/winrm v0.0.0-20180224160350-7e40f93ae939
-	github.com/mattn/go-tty v0.0.0-20190407112021-83fae09cc007
+	github.com/mattn/go-tty v0.0.0-20190424173100-523744f04859
 	github.com/miekg/dns v1.1.1 // indirect
 	github.com/mitchellh/cli v1.0.0
 	github.com/mitchellh/go-fs v0.0.0-20180402234041-7b48fa161ea7

go.sum

@@ -231,8 +231,8 @@ github.com/mattn/go-isatty v0.0.4 h1:bnP0vzxcAdeI1zdubAl5PjU6zsERjGZb7raWodagDYs
 github.com/mattn/go-isatty v0.0.4/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
 github.com/mattn/go-runewidth v0.0.4 h1:2BvfKmzob6Bmd4YsL0zygOqfdFnK7GR4QL06Do4/p7Y=
 github.com/mattn/go-runewidth v0.0.4/go.mod h1:LwmH8dsx7+W8Uxz3IHJYH5QSwggIsqBzpuz5H//U1FU=
-github.com/mattn/go-tty v0.0.0-20190407112021-83fae09cc007 h1:xjZxmVDmDZoEsl2gV0qD0pyBH+wXmJIZd27wsNFphJk=
+github.com/mattn/go-tty v0.0.0-20190424173100-523744f04859 h1:smQbSzmT3EHl4EUwtFwFGmGIpiYgIiiPeVv1uguIQEE=
-github.com/mattn/go-tty v0.0.0-20190407112021-83fae09cc007/go.mod h1:XPvLUNfbS4fJH25nqRHfWLMa1ONC8Amw+mIA639KxkE=
+github.com/mattn/go-tty v0.0.0-20190424173100-523744f04859/go.mod h1:XPvLUNfbS4fJH25nqRHfWLMa1ONC8Amw+mIA639KxkE=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
 github.com/microcosm-cc/bluemonday v1.0.1/go.mod h1:hsXNsILzKxV+sX77C5b8FSuKF00vh2OMYv+xgHpAMF4=
 github.com/miekg/dns v1.0.14/go.mod h1:W1PPwlIAgtquWBMBEV9nkV9Cazfe8ScdGz/Lj7v3Nrg=

vendor/github.com/mattn/go-tty/tty.go

@@ -38,6 +38,10 @@ func (tty *TTY) Size() (int, int, error) {
 	return tty.size()
 }
 
+func (tty *TTY) SizePixel() (int, int, int, int, error) {
+	return tty.sizePixel()
+}
+
 func (tty *TTY) Input() *os.File {
 	return tty.input()
 }
@@ -115,6 +119,6 @@ type WINSIZE struct {
 	H int
 }
 
-func (tty *TTY) SIGWINCH() chan WINSIZE {
+func (tty *TTY) SIGWINCH() <-chan WINSIZE {
 	return tty.sigwinch()
 }

vendor/github.com/mattn/go-tty/tty_plan9.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"os"
 	"syscall"
+	"errors"
 )
 
 type TTY struct {
@@ -54,6 +55,11 @@ func (tty *TTY) size() (int, int, error) {
 	return 80, 24, nil
 }
 
+func (tty *TTY) sizePixel() (int, int, int, int, error) {
+	x, y, _ := tty.size()
+	return x, y, -1, -1, errors.New("no implemented method for querying size in pixels on Plan 9")
+}
+
 func (tty *TTY) input() *os.File {
 	return tty.in
 }

vendor/github.com/mattn/go-tty/tty_unix.go

@@ -18,7 +18,6 @@ type TTY struct {
 	bin     *bufio.Reader
 	out     *os.File
 	termios syscall.Termios
-	ws      chan WINSIZE
 	ss      chan os.Signal
 }
 
@@ -48,24 +47,8 @@ func open() (*TTY, error) {
 		return nil, err
 	}
 
-	tty.ws = make(chan WINSIZE)
 	tty.ss = make(chan os.Signal, 1)
-	signal.Notify(tty.ss, syscall.SIGWINCH)
+
-	go func() {
-		defer close(tty.ws)
-		for sig := range tty.ss {
-			switch sig {
-			case syscall.SIGWINCH:
-				if w, h, err := tty.size(); err == nil {
-					tty.ws <- WINSIZE{
-						W: w,
-						H: h,
-					}
-				}
-			default:
-			}
-		}
-	}()
 	return tty, nil
 }
 
@@ -86,11 +69,16 @@ func (tty *TTY) close() error {
 }
 
 func (tty *TTY) size() (int, int, error) {
+	x, y, _, _, err := tty.sizePixel()
+	return x, y, err
+}
+
+func (tty *TTY) sizePixel() (int, int, int, int, error) {
 	var dim [4]uint16
 	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(tty.out.Fd()), uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(&dim)), 0, 0, 0); err != 0 {
-		return -1, -1, err
+		return -1, -1, -1, -1, err
 	}
-	return int(dim[1]), int(dim[0]), nil
+	return int(dim[1]), int(dim[0]), int(dim[2]), int(dim[3]), nil
 }
 
 func (tty *TTY) input() *os.File {
@@ -127,6 +115,28 @@ func (tty *TTY) raw() (func() error, error) {
 	}, nil
 }
 
-func (tty *TTY) sigwinch() chan WINSIZE {
+func (tty *TTY) sigwinch() <-chan WINSIZE {
-	return tty.ws
+	signal.Notify(tty.ss, syscall.SIGWINCH)
+
+	ws := make(chan WINSIZE)
+	go func() {
+		defer close(ws)
+		for sig := range tty.ss {
+			if sig != syscall.SIGWINCH {
+				continue
+			}
+
+			w, h, err := tty.size()
+			if err != nil {
+				continue
+			}
+			// send but do not block for it
+			select {
+			case ws <- WINSIZE{W: w, H: h}:
+			default:
+			}
+
+		}
+	}()
+	return ws
 }

vendor/github.com/mattn/go-tty/tty_windows.go

@@ -3,7 +3,9 @@
 package tty
 
 import (
+	"context"
 	"os"
+	"errors"
 	"syscall"
 	"unsafe"
 
@@ -122,11 +124,13 @@ type charInfo struct {
 }
 
 type TTY struct {
-	in  *os.File
+	in                *os.File
-	out *os.File
+	out               *os.File
-	st  uint32
+	st                uint32
-	rs  []rune
+	rs                []rune
-	ws  chan WINSIZE
+	ws                chan WINSIZE
+	sigwinchCtx       context.Context
+	sigwinchCtxCancel context.CancelFunc
 }
 
 func readConsoleInput(fd uintptr, record *inputRecord) (err error) {
@@ -183,6 +187,7 @@ func open() (*TTY, error) {
 	procSetConsoleMode.Call(h, uintptr(st))
 
 	tty.ws = make(chan WINSIZE)
+	tty.sigwinchCtx, tty.sigwinchCtxCancel = context.WithCancel(context.Background())
 
 	return tty, nil
 }
@@ -206,10 +211,24 @@ func (tty *TTY) readRune() (rune, error) {
 	switch ir.eventType {
 	case windowBufferSizeEvent:
 		wr := (*windowBufferSizeRecord)(unsafe.Pointer(&ir.event))
-		tty.ws <- WINSIZE{
+		ws := WINSIZE{
 			W: int(wr.size.x),
 			H: int(wr.size.y),
 		}
+
+		if err := tty.sigwinchCtx.Err(); err != nil {
+			// closing
+			// the following select might panic without this guard close
+			return 0, err
+		}
+
+		select {
+		case tty.ws <- ws:
+		case <-tty.sigwinchCtx.Done():
+			return 0, tty.sigwinchCtx.Err()
+		default:
+			return 0, nil // no one is currently trying to read
+		}
 	case keyEvent:
 		kr := (*keyEventRecord)(unsafe.Pointer(&ir.event))
 		if kr.keyDown != 0 {
@@ -307,8 +326,9 @@ func (tty *TTY) readRune() (rune, error) {
 }
 
 func (tty *TTY) close() error {
-	close(tty.ws)
 	procSetConsoleMode.Call(tty.in.Fd(), uintptr(tty.st))
+	tty.sigwinchCtxCancel()
+	close(tty.ws)
 	return nil
 }
 
@@ -321,6 +341,15 @@ func (tty *TTY) size() (int, int, error) {
 	return int(csbi.window.right - csbi.window.left + 1), int(csbi.window.bottom - csbi.window.top + 1), nil
 }
 
+func (tty *TTY) sizePixel() (int, int, int, int, error) {
+	x, y, err := tty.size()
+	if err != nil {
+		x = -1
+		y = -1
+	}
+	return x, y, -1, -1, errors.New("no implemented method for querying size in pixels on Windows")
+}
+
 func (tty *TTY) input() *os.File {
 	return tty.in
 }
@@ -349,6 +378,6 @@ func (tty *TTY) raw() (func() error, error) {
 	}, nil
 }
 
-func (tty *TTY) sigwinch() chan WINSIZE {
+func (tty *TTY) sigwinch() <-chan WINSIZE {
 	return tty.ws
 }

vendor/modules.txt

@@ -299,7 +299,7 @@ github.com/mattn/go-colorable
 github.com/mattn/go-isatty
 # github.com/mattn/go-runewidth v0.0.4
 github.com/mattn/go-runewidth
-# github.com/mattn/go-tty v0.0.0-20190407112021-83fae09cc007
+# github.com/mattn/go-tty v0.0.0-20190424173100-523744f04859
 github.com/mattn/go-tty
 # github.com/mitchellh/cli v1.0.0
 github.com/mitchellh/cli