set an ALPN value in the tls.Config

crypto.go

@@ -21,6 +21,7 @@ import (
 
 const certValidityPeriod = 100 * 365 * 24 * time.Hour // ~100 years
 const certificatePrefix = "libp2p-tls-handshake:"
+const alpn string = "libp2p"
 
 var extensionID = getPrefixedExtensionID([]int{1, 1})
 
@@ -50,6 +51,7 @@ func NewIdentity(privKey ic.PrivKey) (*Identity, error) {
 			VerifyPeerCertificate: func(_ [][]byte, _ [][]*x509.Certificate) error {
 				panic("tls config not specialized for peer")
 			},
+			NextProtos:             []string{alpn},
 			SessionTicketsDisabled: true,
 		},
 	}, nil