terminal: Use go-colorable

Add fallback to display colors on Windows.

terminal/terminal_windows.go

@@ -1,31 +1,35 @@
 package terminal
 
 import (
+	"io"
 	"os"
 	"strings"
 	"syscall"
+
+	"github.com/mattn/go-colorable"
 )
 
-// supportsEscapeCodes returns true if console handles escape codes.
-func supportsEscapeCodes() bool {
-	if strings.ToLower(os.Getenv("TERM")) == "dumb" {
-		return false
-	}
+// getColorableWriter returns two values. First is Writer supported colors.
+// If return nil, colors will be disabled.
+func getColorableWriter() io.Writer {
 	if strings.ToLower(os.Getenv("ConEmuANSI")) == "on" {
 		// The ConEmu terminal is installed. Use it.
-		return true
+		return os.Stdout
 	}
 
 	const ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x0004
 
 	h, err := syscall.GetStdHandle(syscall.STD_OUTPUT_HANDLE)
 	if err != nil {
-		return false
+		return os.Stdout
 	}
 	var m uint32
 	err = syscall.GetConsoleMode(h, &m)
 	if err != nil {
-		return false
+		return os.Stdout
 	}
-	return m&ENABLE_VIRTUAL_TERMINAL_PROCESSING != 0
+	if m&ENABLE_VIRTUAL_TERMINAL_PROCESSING != 0 {
+		return os.Stdout
+	}
+	return colorable.NewColorableStdout()
 }