package middleware import ( "net" "time" cache "github.com/patrickmn/go-cache" ) var ipToHosts = cache.New(60*time.Minute, 30*time.Minute) // GetHostsForIP returns all host names for the given IP (if cached). func GetHostsForIP(ip string) []string { hosts, found := ipToHosts.Get(ip) if !found { hosts = findHostsForIP(ip) } if hosts == nil { return nil } return hosts.([]string) } // Finds all host names for the given IP func findHostsForIP(ip string) []string { hosts, err := net.LookupAddr(ip) if err != nil { return nil } if len(hosts) == 0 { return nil } // Cache host names ipToHosts.Set(ip, hosts, cache.DefaultExpiration) return hosts }