Try to avoid panicking in PosixParser if there's no /dev/tty.

When using go-prompt before /dev/ is populated, it will panic() from
NewStandardInputParser() because /dev/ isn't populated yet.

This will use stdin (fd 0) as a fallback if /dev/tty doesn't exist.

Furthermore GetWinSize() will return the default console size if the
IOCTL call fails. This can happen if the default stdin is not a
terminal, but a pipe as fixed in commit 846777c and described in
issue c-bata#88.

input_posix.go

@@ -3,6 +3,7 @@
 package prompt
 
 import (
+ "os"
  "syscall"
 
  "github.com/c-bata/go-prompt/internal/term"
@@ -54,7 +55,12 @@ func (t *PosixParser) Read() ([]byte, error) {
 func (t *PosixParser) GetWinSize() *WinSize {
  ws, err := unix.IoctlGetWinsize(t.fd, unix.TIOCGWINSZ)
  if err != nil {
- panic(err)
+ // If this errors, we simply return the default window size as
+ // it's our best guess.
+ return &WinSize{
+ Row: 25,
+ Col: 80,
+ }
  }
  return &WinSize{
  Row: ws.Row,
@@ -67,7 +73,9 @@ var _ ConsoleParser = &PosixParser{}
 // NewStandardInputParser returns ConsoleParser object to read from stdin.
 func NewStandardInputParser() *PosixParser {
  in, err := syscall.Open("/dev/tty", syscall.O_RDONLY, 0)
- if err != nil {
+ if os.IsNotExist(err) {
+ in = syscall.Stdin
+ } else if err != nil {
  panic(err)
  }