Added Close request to gRPC Monitor API

Author: cmaglie

commands/daemon/daemon.go

@@ -469,6 +469,11 @@ func (s *ArduinoCoreServerImpl) Monitor(stream rpc.ArduinoCoreService_MonitorSer
 					}
 				}
 			}
+			if close := msg.GetClose(); close {
+				if err := portProxy.Close(); err != nil {
+					logrus.WithError(err).Debug("Error closing monitor port")
+				}
+			}
 			tx := msg.GetTxData()
 			for len(tx) > 0 {
 				n, err := portProxy.Write(tx)

rpc/cc/arduino/cli/commands/v1/monitor.pb.go

@@ -30,6 +30,10 @@ message MonitorRequest {
     bytes tx_data = 2;
     // Port configuration, contains settings of the port to be changed
     MonitorPortConfiguration updated_configuration = 3;
+    // Close message, set to true to gracefully close a port (this ensure
+    // that the gRPC streaming call is closed by the daemon AFTER the port
+    // has been successfully closed)
+    bool close = 4;
   }
 }