Specify a "Sudo password:" prompt for sudo

Fixes #178
Closes #185

main.go

@@ -16,10 +16,12 @@ import (
 	"net/url"
 	"os"
 	"os/exec"
+	"os/user"
 	"path/filepath"
 	"regexp"
 	"runtime"
 	"strings"
+	"sync"
 
 	"golang.org/x/net/idna"
 )
@@ -345,3 +347,18 @@ func binaryExists(name string) bool {
 	_, err := exec.LookPath(name)
 	return err == nil
 }
+
+var sudoWarningOnce sync.Once
+
+func commandWithSudo(cmd ...string) *exec.Cmd {
+	if u, err := user.Current(); err == nil && u.Uid == "0" {
+		return exec.Command(cmd[0], cmd[1:]...)
+	}
+	if !binaryExists("sudo") {
+		sudoWarningOnce.Do(func() {
+			log.Println(`Warning: "sudo" is not available, and mkcert is not running as root. The (un)install operation might fail. ⚠️`)
+		})
+		return exec.Command(cmd[0], cmd[1:]...)
+	}
+	return exec.Command("sudo", append([]string{"--prompt=Sudo password:", "--"}, cmd...)...)
+}