Use regexp2

go.mod

@@ -7,4 +7,7 @@ require (
 	gopkg.in/neurosnap/sentences.v1 v1.0.7
 )
 
-require github.com/neurosnap/sentences v1.1.2 // indirect
+require (
+	github.com/errata-ai/regexp2 v1.7.0 // indirect
+	github.com/neurosnap/sentences v1.1.2 // indirect
+)

go.sum

@@ -1,3 +1,5 @@
+github.com/errata-ai/regexp2 v1.7.0 h1:N+weOlhwTd5iyDTcTCAMljXnfzkftcOZrdXno6G+QPM=
+github.com/errata-ai/regexp2 v1.7.0/go.mod h1:59rO+jaxayJPF1WKI5m9R5F3Y3zR2Wn0DHnQbxtPm4A=
 github.com/montanaflynn/stats v0.7.1 h1:etflOAAHORrCC44V+aR6Ftzort912ZU+YLiSTuV8eaE=
 github.com/montanaflynn/stats v0.7.1/go.mod h1:etXPPgVO6n31NxCd9KQUMvCM+ve0ruNzt6R8Bnaayow=
 github.com/neurosnap/sentences v1.1.2 h1:iphYOzx/XckXeBiLIUBkPu2EKMJ+6jDbz/sLJZ7ZoUw=

strcase/sentence.go

@@ -2,19 +2,19 @@ package strcase
 
 import (
 	"fmt"
-	"regexp"
 	"strings"
 
+	"github.com/errata-ai/regexp2"
 	"github.com/jdkato/twine/internal"
 )
 
-var reNumberList = regexp.MustCompile(`\d+\.`)
+var reNumberList = regexp2.MustCompileStd(`\d+\.`)
 var defaultSentOpts = CaseOpts{
 	vocab: []string{},
 	indicator: func(word string, idx int) bool {
 		if strings.HasSuffix(word, ":") {
 			return true
-		} else if idx == 0 && reNumberList.MatchString(word) {
+		} else if idx == 0 && reNumberList.MatchStringStd(word) {
 			return true
 		}
 		return false
@@ -51,7 +51,7 @@ func (sc *SentenceConverter) Convert(s string) string {
 	if len(sc.vocab) > 0 {
 		ps = fmt.Sprintf(`\b(?:%s)\b|%s`, strings.Join(sc.vocab, "|"), ps)
 	}
-	re := regexp.MustCompile(`(?i)` + ps)
+	re := regexp2.MustCompileStd(`(?i)` + ps)
 
 	tokens := re.FindAllString(s, -1)
 	for i, token := range tokens {
@@ -74,7 +74,7 @@ func (sc *SentenceConverter) Convert(s string) string {
 
 func (sc *SentenceConverter) inVocab(s string) string {
 	for _, token := range sc.vocab {
-		matched, _ := regexp.MatchString(token, s)
+		matched, _ := regexp2.MatchString(token, s)
 		if strings.ToLower(token) == strings.ToLower(s) {
 			return token
 		} else if matched {

strcase/title.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 	"unicode/utf8"
 
+	"github.com/errata-ai/regexp2"
 	"github.com/jdkato/twine/internal"
 	"github.com/jdkato/twine/nlp/tag"
 )
@@ -102,7 +103,7 @@ func (tc *TitleConverter) Convert(s string) string {
 
 func (tc *TitleConverter) inVocab(s string) string {
 	for _, token := range tc.vocab {
-		matched, _ := regexp.MatchString(token, s)
+		matched, _ := regexp2.MatchString(token, s)
 		if strings.ToLower(token) == strings.ToLower(s) {
 			return token
 		} else if matched {