/
dns.go
44 lines (34 loc) · 789 Bytes
/
dns.go
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package main
import (
"context"
"net"
"time"
"github.com/patrickmn/go-cache"
)
type dnsClient struct {
cache *cache.Cache
resolver *net.Resolver
timeout time.Duration
}
func newDNSClient(timeout, dnsCacheTimeout time.Duration) *dnsClient {
var r *net.Resolver
return &dnsClient{
cache: cache.New(dnsCacheTimeout, 1*time.Hour),
resolver: r,
timeout: timeout,
}
}
func (d *dnsClient) ipLookup(ctx context.Context, domain string) ([]string, error) {
val, found := d.cache.Get(domain)
if found {
return val.([]string), nil
}
ctx2, cancel := context.WithTimeout(ctx, d.timeout)
defer cancel()
addr, err := d.resolver.LookupHost(ctx2, domain)
if err != nil {
return nil, err
}
d.cache.Set(domain, addr, cache.DefaultExpiration)
return addr, nil
}