Ros2: nav2_map_server can not load map?

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Operating System: Ubuntu 18.04

ROS2 Dashing

Steps to reproduce issue

As we follow https://github.com/ros-planning/navig... to load map by ros2 navigation, the map not uplaod when we run

$ ros2 run nav2_map_server map_server __params:=map_server_params.yaml

We now show topics in

$ ros2 topic list 
/clock
/map_server/transition_event 
/parameter_events
/rosout
/tf
$ ros2 node list
/map_server

Expected behavior

Can display map in RVIZ2

Actual behavior

Unable to display map in RVIZ2.