Parse time duration as string - either assume seconds or parse string as rich format e.g., 5m 30s, etc.

main.go

package main

import (
	"fmt"
	"strconv"
	"time"
)

func parseExpiry(s string) (time.Duration, error) {
	var t time.Duration

	n, err := strconv.ParseInt(s, 10, 64)
	if err == nil {
		t = time.Duration(n) * time.Second
	} else {
		t, err = time.ParseDuration(s)
	}
	if err != nil {
		return 0, err
	}
	if t < 0 {
		t = -t
	}
	return t, nil
}

func main() {
	// Assume seconds by default.
	fmt.Println(parseExpiry("300"))
	// Rich string parsing.
	fmt.Println(parseExpiry("5m"))
	// Handle negative values.
	fmt.Println(parseExpiry("-2"))
	// Return error on parsing failure.
	fmt.Println(parseExpiry("abc"))
}