use go 1.12

Signed-off-by: hongming <talonwan@yunify.com>

vendor/github.com/lucas-clemente/quic-go/internal/handshake/ephermal_cache.go

@@ -0,0 +1,48 @@
+package handshake
+
+import (
+	"sync"
+	"time"
+
+	"github.com/lucas-clemente/quic-go/internal/crypto"
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+)
+
+var (
+	kexLifetime    = protocol.EphermalKeyLifetime
+	kexCurrent     crypto.KeyExchange
+	kexCurrentTime time.Time
+	kexMutex       sync.RWMutex
+)
+
+// getEphermalKEX returns the currently active KEX, which changes every protocol.EphermalKeyLifetime
+// See the explanation from the QUIC crypto doc:
+//
+// A single connection is the usual scope for forward security, but the security
+// difference between an ephemeral key used for a single connection, and one
+// used for all connections for 60 seconds is negligible. Thus we can amortise
+// the Diffie-Hellman key generation at the server over all the connections in a
+// small time span.
+func getEphermalKEX() (crypto.KeyExchange, error) {
+	kexMutex.RLock()
+	res := kexCurrent
+	t := kexCurrentTime
+	kexMutex.RUnlock()
+	if res != nil && time.Since(t) < kexLifetime {
+		return res, nil
+	}
+
+	kexMutex.Lock()
+	defer kexMutex.Unlock()
+	// Check if still unfulfilled
+	if kexCurrent == nil || time.Since(kexCurrentTime) >= kexLifetime {
+		kex, err := crypto.NewCurve25519KEX()
+		if err != nil {
+			return nil, err
+		}
+		kexCurrent = kex
+		kexCurrentTime = time.Now()
+		return kexCurrent, nil
+	}
+	return kexCurrent, nil
+}