If the timeout is set to NoTimeout, make Read wait forever.

Otherwise the maximul allowed timeout is 0x7FFFFFFF milliseconds,
equivalent to about 24.85 days.
This patch will make a transparent repeated read in case this long
timeout should ever happen.

serial_windows.go

@@ -30,6 +30,7 @@ import (
 type windowsPort struct {
 	mu         sync.Mutex
 	handle     windows.Handle
+	hasTimeout bool
 }
 
 func nativeGetPortsList() ([]string, error) {
@@ -72,6 +73,7 @@ func (port *windowsPort) Read(p []byte) (int, error) {
 	}
 	defer windows.CloseHandle(ev.HEvent)
 
+	for {
 		err = windows.ReadFile(port.handle, p, &readed, ev)
 		if err == windows.ERROR_IO_PENDING {
 			err = windows.GetOverlappedResult(port.handle, ev, &readed, true)
@@ -91,8 +93,14 @@ func (port *windowsPort) Read(p []byte) (int, error) {
 		}
 
 		// Timeout
+		port.mu.Lock()
+		hasTimeout := port.hasTimeout
+		port.mu.Unlock()
+		if hasTimeout {
 			return 0, nil
 		}
+	}
+}
 
 func (port *windowsPort) Write(p []byte) (int, error) {
 	var writed uint32
@@ -304,9 +312,12 @@ func (port *windowsPort) SetReadTimeout(timeout time.Duration) error {
 		commTimeouts.ReadTotalTimeoutConstant = uint32(ms)
 	}
 
+	port.mu.Lock()
+	defer port.mu.Unlock()
 	if err := windows.SetCommTimeouts(port.handle, commTimeouts); err != nil {
 		return &PortError{code: InvalidTimeoutValue, causedBy: err}
 	}
+	port.hasTimeout = (timeout != NoTimeout)
 
 	return nil
 }