Fix color support for Windows 10 (stripe#107)

go.mod

@@ -28,6 +28,6 @@ require (
 	github.com/x-cray/logrus-prefixed-formatter v0.5.2
 	golang.org/x/crypto v0.0.0-20190701094942-4def268fd1a4
 	golang.org/x/net v0.0.0-20190724013045-ca1201d0de80 // indirect
-	golang.org/x/sys v0.0.0-20190726091711-fc99dfbffb4e // indirect
+	golang.org/x/sys v0.0.0-20190726091711-fc99dfbffb4e
 	golang.org/x/text v0.3.2 // indirect
 )

pkg/ansi/ansi.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"runtime"
 	"time"
 
 	"github.com/briandowns/spinner"
@@ -84,7 +85,16 @@ func StartSpinner(msg string, w io.Writer) *spinner.Spinner {
 		return nil
 	}
 
-	s := spinner.New(spinner.CharSets[11], 100*time.Millisecond)
+	// See https://github.com/briandowns/spinner#available-character-sets for
+	// list of available charsets
+	charSetIdx := 11
+	if runtime.GOOS == "windows" {
+		// Less fancy, but uses ASCII characters so works with Windows default
+		// console.
+		charSetIdx = 8
+	}
+
+	s := spinner.New(spinner.CharSets[charSetIdx], 100*time.Millisecond)
 	s.Writer = w
 
 	if msg != "" {

pkg/ansi/init_windows.go

@@ -0,0 +1,23 @@
+// +build windows
+
+package ansi
+
+import (
+	"os"
+
+	"golang.org/x/sys/windows"
+)
+
+// enableAnsiColors enables support for ANSI color sequences in Windows
+// default console. Note that this only works with Windows 10.
+func enableAnsiColors() {
+	stdout := windows.Handle(os.Stdout.Fd())
+	var originalMode uint32
+
+	windows.GetConsoleMode(stdout, &originalMode)
+	windows.SetConsoleMode(stdout, originalMode|windows.ENABLE_VIRTUAL_TERMINAL_PROCESSING)
+}
+
+func init() {
+	enableAnsiColors()
+}