Use enumeration for Darwin, which requires CGO when building.

- Tkeyclient does not support building static binaries for Darwin, it
  requires CGO to enable enumeration of connected serial devices. In the
  short term we enable CGO for Darwin before we can find another
  reliable solution. See issue #13.

go.mod

@@ -6,12 +6,12 @@ require (
 	github.com/spf13/pflag v1.0.5
 	github.com/tillitis/tkeyclient v1.0.0
 	github.com/tillitis/tkeysign v1.0.0
-	go.bug.st/serial v1.6.2
 	gopkg.in/yaml.v2 v2.4.0
 )
 
 require (
 	github.com/creack/goselect v0.1.2 // indirect
+	go.bug.st/serial v1.6.2 // indirect
 	golang.org/x/crypto v0.22.0 // indirect
 	golang.org/x/sys v0.19.0 // indirect
 )

internal/tkey/tkey.go

@@ -25,7 +25,6 @@ import (
 	"os"
 	"os/signal"
 
-	"github.com/tillitis/tkey-verification/internal/util"
 	"github.com/tillitis/tkeyclient"
 	"github.com/tillitis/tkeysign"
 )
@@ -66,7 +65,7 @@ func NewTKey(devPath string, verbose bool) (*TKey, error) {
 	}
 
 	if devPath == "" {
-		devPath, err = util.DetectSerialPort(true)
+		devPath, err = tkeyclient.DetectSerialPort(true)
 		if err != nil {
 			return nil, ErrNoDevice
 		}