Add function SetReadTimeoutNoErr

Same functionality as SetReadTimeout except that it does not return any
errors. This makes it more easily used in combination with defer. The
potential errors from the underlying serial library are handled
(invalidTimeoutValue), but a panic is added to notify about potential
API changes.

Deprecation notice added for SetReadTimeout

tkeyclient.go

@@ -108,10 +108,13 @@ func (tk TillitisKey) Close() error {
 	return nil
 }
 
-// SetReadTimeout sets the timeout of the underlying serial connection
-// to the TKey. Pass 0 seconds to not have any timeout. Note that the
-// timeout implemented in the serial lib only works for simple Read().
-// E.g. io.ReadFull() will Read() until the buffer is full.
+// SetReadTimeout sets the timeout of the underlying serial connection to the
+// TKey. Pass 0 seconds to not have any timeout. Note that the timeout
+// implemented in the serial lib only works for simple Read(). E.g.
+// io.ReadFull() will Read() until the buffer is full.
+//
+// Deprecated: use SetReadTimeoutNoErr, which can more easily be used with
+// defer.
 func (tk TillitisKey) SetReadTimeout(seconds int) error {
 	var t time.Duration = -1
 	if seconds > 0 {
@@ -123,6 +126,26 @@ func (tk TillitisKey) SetReadTimeout(seconds int) error {
 	return nil
 }
 
+// SetReadTimeoutNoErr sets the timeout, in seconds, of the underlying
+// serial connection to the TKey. Pass 0 seconds to not have any
+// timeout.
+//
+// Note that the timeout only works for simple Read(). E.g.
+// io.ReadFull() will still read until the buffer is full.
+func (tk TillitisKey) SetReadTimeoutNoErr(seconds int) {
+	var t time.Duration = -1 // disables timeout
+	if seconds > 0 {
+		t = time.Duration(seconds) * time.Second
+	}
+	if err := tk.conn.SetReadTimeout(t); err != nil {
+		// err != nil exclusively on invalid values of t,
+		// which is handled before the call. Panic only
+		// possible for API change in go.bug.st/serial
+		panic(fmt.Sprintf("SetReadTimeout: %v", err))
+	}
+	return
+}
+
 type NameVersion struct {
 	Name0   string
 	Name1   string