sample-lnd.conf: describe grpc keepalive params

sample-lnd.conf

@@ -1501,3 +1501,21 @@ litecoin.node=ltcd
 ; are sent over a short period.
 ; htlcswitch.mailboxdeliverytimeout=60s
 
+[grpc]
+
+; How long the server waits on a gRPC stream with no activity before pinging the
+; client. Valid time units are {s, m, h}. Default: 1m
+; grpc.server-ping-time=1m
+
+; How long the server waits for the response from the client for the keepalive
+; ping response. Valid time units are {s, m, h}. Default: 20s
+; grpc.server-ping-timeout=20s
+
+; The minimum amount of time the client should wait before sending a keepalive
+; ping. Valid time units are {s, m, h}. Default: 5s
+; grpc.client-ping-min-wait=5s
+
+; If true, the server allows keepalive pings from the client even when there are
+; no active gRPC streams. This might be useful to keep the underlying HTTP/2
+; connection open for future requests.
+; grpc.client-allow-ping-without-stream=false