Make regexp top-level as per PR comments

src/github.com/matrix-org/go-neb/services/github/github.go

@@ -14,7 +14,7 @@ import (
 
 // Matches alphanumeric then a /, then more alphanumeric then a #, then a number.
 // E.g. owner/repo#11 (issue/PR numbers) - Captured groups for owner/repo/number
-const ownerRepoIssueRegex = "([A-z0-9-_]+)/([A-z0-9-_]+)#([0-9]+)"
+var ownerRepoIssueRegex = regexp.MustCompile("([A-z0-9-_]+)/([A-z0-9-_]+)#([0-9]+)")
 
 type githubService struct {
 	id     string
@@ -31,7 +31,7 @@ func (s *githubService) Plugin(roomID string) plugin.Plugin {
 		Commands: []plugin.Command{},
 		Expansions: []plugin.Expansion{
 			plugin.Expansion{
-				Regexp: regexp.MustCompile(ownerRepoIssueRegex),
+				Regexp: ownerRepoIssueRegex,
 				Expand: func(roomID, matchingText string) interface{} {
 					cli := githubClient("")
 					owner, repo, num, err := ownerRepoNumberFromText(matchingText)
@@ -78,10 +78,8 @@ func githubClient(token string) *github.Client {
 // ownerRepoNumberFromText parses a GH issue string that looks like 'owner/repo#11'
 // into its constituient parts. Returns: owner, repo, issue#.
 func ownerRepoNumberFromText(ownerRepoNumberText string) (string, string, int, error) {
-	// TODO: cache this?
-	re := regexp.MustCompile(ownerRepoIssueRegex)
 	// [full_string, owner, repo, issue_number]
-	groups := re.FindStringSubmatch(ownerRepoNumberText)
+	groups := ownerRepoIssueRegex.FindStringSubmatch(ownerRepoNumberText)
 	if len(groups) != 4 {
 		return "", "", 0, fmt.Errorf("No match found for '%s'", ownerRepoNumberText)
 	}