Golang regex get value inside parentheses - regex

Question

Code:
package main
import (
"fmt"
"regexp"
)
func main() {
r := regexp.MustCompile(`((.*))`)
s := `(tag)SomeText`
res := r.FindStringSubmatch(s)
fmt.Println(res[1])
}
How to Get Value inside parentheses?

Answer 1

1- While it is simple using regex (try it on The Go Playground):
package main
import (
"fmt"
"regexp"
)
var rgx = regexp.MustCompile(`\((.*?)\)`)
func main() {
s := `(tag)SomeText`
rs := rgx.FindStringSubmatch(s)
fmt.Println(rs[1])
}
output:
tag
2- but sometimes using strings.Index is fast enough (try it on The Go Playground):
package main
import (
"fmt"
"strings"
)
func match(s string) string {
i := strings.Index(s, "(")
if i >= 0 {
j := strings.Index(s, ")")
if j >= 0 {
return s[i+1 : j]
}
}
return ""
}
func main() {
s := `Some(tag)Text`
r := match(s)
fmt.Println(r)
}
output:
tag
3- This simple benchmark shows using regex takes 931ms and using strings.Index takes 43ms for 1000000 iterations.
package main
import (
"fmt"
"regexp"
"strings"
"time"
)
var rgx = regexp.MustCompile(`\((.*?)\)`)
const n = 1000000
func main() {
var rs []string
var r string
s := `(tag)SomeText`
t := time.Now()
for i := 0; i < n; i++ {
rs = rgx.FindStringSubmatch(s)
}
fmt.Println(time.Since(t))
fmt.Println(rs[1]) // [(tag) tag]
t = time.Now()
for i := 0; i < n; i++ {
r = match(s)
}
fmt.Println(time.Since(t))
fmt.Println(r)
}
func match(s string) string {
i := strings.Index(s, "(")
if i >= 0 {
j := strings.Index(s, ")")
if j >= 0 {
return s[i+1 : j]
}
}
return ""
}

Answer 2

I got My problem solved by this regex
r := regexp.MustCompile(`\((.*?)\)`)

Answer 3

Refer to answers, I made my version of the code.
link: https://play.golang.org/p/b82iPZGU1gw
package main
import (
"fmt"
"strings"
)
func match(start, end, s string) string {
i := strings.Index(s, start)
if i >= 0 {
j := strings.Index(s[i:], end)
if j >= 0 {
return s[i+len(start) : i+j]
}
}
return ""
}
func main() {
errText := `facebook: Error validating access token: Session has expired on Tuesday, 28-Jul-20 22:00:00 PDT. The current time is Wednesday, 29-Jul-20 17:55:22 PDT. (code: 190; error_subcode: 463, error_user_title: , error_user_msg: )`
start := "code: "
end := ";"
r := match(start, end, errText)
fmt.Println(r)
}