Add http/2 support to API server (#5149)

fix issue #5148

Signed-off-by: Kamil Madac <kamil.madac@gmail.com>

pkg/cluster/https.go

@@ -53,6 +53,7 @@ func (c *Cluster) newListener(ctx context.Context) (net.Listener, http.Handler,
 			ClientAuth:   tls.RequestClientCert,
 			MinVersion:   c.config.TLSMinVersion,
 			CipherSuites: c.config.TLSCipherSuites,
+			NextProtos:   []string{"h2", "http/1.1"},
 		},
 		RegenerateCerts: func() bool {
 			const regenerateDynamicListenerFile = "dynamic-cert-regenerate"