import "github.com/abursavich/nett"
Package nett steals from the standard library's net package and provides a dialer with a pluggable host resolver.
dialer := &nett.Dialer{
// Cache successful DNS lookups for five minutes
// using DefaultResolver to fill the cache.
Resolver: &nett.CacheResolver{TTL: 5 * time.Minute},
// Concurrently dial an IPv4 and an IPv6 address and
// return the connection that is established first.
IPFilter: nett.DualStack,
// Give up after ten seconds including DNS resolution.
Timeout: 10 * time.Second,
}
client := &http.Client{
Transport: &http.Transport{
// Use the Dialer.
Dial: dialer.Dial,
},
}
urls := []string{
"https://www.google.com/search?q=golang",
"https://www.google.com/search?q=godoc",
"https://www.google.com/search?q=golang-nuts",
}
for _, url := range urls {
resp, err := client.Get(url)
if err != nil {
panic(err)
}
io.Copy(ioutil.Discard, resp.Body)
resp.Body.Close()
}func DualStack(ips []net.IP) []net.IPDualStack selects the first IPv4 address and IPv6 address in ips.
type CacheResolver struct {
// Resolver resolves hosts that are not cached.
// If Resolver is nil, DefaultResolver will be used.
Resolver Resolver
// TTL is the time to live for resolved hosts.
// If TTL is zero, cached hosts do not expire.
TTL time.Duration
// contains filtered or unexported fields
}CacheResolver looks up the IP addresses of a host and caches successful results.
func (r *CacheResolver) Resolve(host string) ([]net.IP, error)Resolve returns a host's IP addresses.
type Dialer struct {
// Timeout is the maximum amount of time a dial will wait for
// a connect to complete. If Deadline is also set, it may fail
// earlier.
//
// The default is no timeout.
//
// With or without a timeout, the operating system may impose
// its own earlier timeout. For instance, TCP timeouts are
// often around 3 minutes.
Timeout time.Duration
// Deadline is the absolute point in time after which dials
// will fail. If Timeout is set, it may fail earlier.
//
// Zero means no deadline, or dependent on the operating system
// as with the Timeout option.
Deadline time.Time
// LocalAddr is the local address to use when dialing an
// address. The address must be of a compatible type for the
// network being dialed.
//
// If nil, a local address is automatically chosen.
LocalAddr net.Addr
// Resolver is used to resolve IP addresses from domain names.
//
// If nil, DefaultResolver will be used.
Resolver Resolver
// IPFilter selects addresses from those available after
// resolving a host to a set of supported IPs.
//
// When dialing a TCP connection if multiple addresses are
// returned, then a connection will attempt to be established
// with each address and the first that succeeds will be returned.
// With any other type of connection, only the first address
// returned will be dialed.
//
// If nil, a single address is selected.
IPFilter func(ips []net.IP) []net.IP
// KeepAlive specifies the keep-alive period for an active
// network connection.
//
// If zero, keep-alives are not enabled. Network protocols
// that do not support keep-alives ignore this field.
//
// Only functional for go1.3+.
KeepAlive time.Duration
}A Dialer contains options for connecting to an address.
func (d *Dialer) Dial(network, address string) (net.Conn, error)Dial connects to the address on the named network.
Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only), "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4" (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and "unixpacket".
For TCP and UDP networks, addresses have the form host:port. If host is a literal IPv6 address it must be enclosed in square brackets as in "[::1]:80" or "[ipv6-host%zone]:80". The functions JoinHostPort and SplitHostPort manipulate addresses in this form.
Examples:
Dial("tcp", "12.34.56.78:80")
Dial("tcp", "google.com:http")
Dial("tcp", "[2001:db8::1]:http")
Dial("tcp", "[fe80::1%lo0]:80")
For IP networks, the network must be "ip", "ip4" or "ip6" followed by a colon and a protocol number or name and the addr must be a literal IP address.
Examples:
Dial("ip4:1", "127.0.0.1")
Dial("ip6:ospf", "::1")
For Unix networks, the address must be a file system path.
type Resolver interface {
// Resolve looks up the given host and returns its IP addresses.
Resolve(host string) ([]net.IP, error)
}Resolver is an interface representing the ability to lookup the IP addresses of a host. It may return results containing networks not supported by the platform.
A Resolver must be safe for concurrent use by multiple goroutines.
var DefaultResolver Resolver = defaultResolver{}DefaultResolver is the default Resolver.
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