Do not preallocate regex in init program

We are trying to speed up the startup of container applications
by not MustCompiling in init but waiting until first use of application.

While this will only speed up start by a couple of microseconds, the
more we get rid of the faster the apps will start.

Signed-off-by: Daniel J Walsh <[email protected]>

Author: rhatdan

gpg.go

@@ -24,6 +24,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
@@ -310,9 +311,15 @@ func resolveRecipients(gc GPGClient, recipients []string) []string {
 	return result
 }
 
-var emailPattern = regexp.MustCompile(`uid\s+\[.*\]\s.*\s<(?P<email>.+)>`)
+var (
+	onceRegexp   sync.Once
+	emailPattern *regexp.Regexp
+)
 
 func extractEmailFromDetails(details []byte) string {
+	onceRegexp.Do(func() {
+		emailPattern = regexp.MustCompile(`uid\s+\[.*\]\s.*\s<(?P<email>.+)>`)
+	})
 	loc := emailPattern.FindSubmatchIndex(details)
 	if len(loc) == 0 {
 		return ""