feat(123): support mail login (close #2218 pr #2276)

pkg/utils/email.go

@@ -0,0 +1,9 @@
+package utils
+
+import "regexp"
+
+func IsEmailFormat(email string) bool {
+	pattern := `^[0-9a-z][_.0-9a-z-]{0,31}@([0-9a-z][0-9a-z-]{0,30}[0-9a-z]\.){1,4}[a-z]{2,4}$`
+	reg := regexp.MustCompile(pattern)
+	return reg.MatchString(email)
+}