Setting a goal point where is an obstacle

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I know of at least two existing packages that could provide the functionality that you want :

• Carrot Planner
• asr_navfn

Carrot Planner will move your robot straight to the goal position and stop it in front of any obstacle.

I quote from their wiki page:

The planner takes a goal point from an external user, checks if the user-specified goal is in an obstacle, and if it is, it walks back along the vector between the user-specified goal and the robot until a goal point that is not in an obstacle is found. It then passes this goal point on as a plan to a local planner or controller. In this way, the carrot planner allows the robot to get as close to a user-specified goal point as possible.

To test it you just have to add the following code to the launch file where you start move_base:

<param name="base_global_planner" value="carrot_planner/CarrotPlanner" />

This is an exemplary launch file:

<?xml version="1.0"?>
<launch>

  <!-- Start move_base (nav stack) node and load config files -->    
  <node pkg="move_base" type="move_base" respawn="false" name="move_base" output="screen">
    <rosparam file="$(find your_pkg)/config/costmap_common_params.yaml" command="load" ns="global_costmap" />
    <rosparam file="$(find your_pkg)/config/costmap_common_params.yaml" command="load" ns="local_costmap" />
    <rosparam file="$(find your_pkg)/config/local_costmap_params.yaml" command="load" />
    <rosparam file="$(find your_pkg)/config/global_costmap_params.yaml" command="load" />
    <rosparam file="$(find your_pkg)/config/base_local_planner_params.yaml" command="load" />

    <!-- Set the global planner: -->
    <param name="base_global_planner" value="carrot_planner/CarrotPlanner" /> 

  </node>

</launch>

The second option I know, the asr_navfn package, is also a global planner that can navigate your robot to the closest free space if the desired destination is in an obstacle. The main benefit is that it is not limited to a stright line path, as in Carrot Planner.

The image on their wiki page is pretty self-explanatory:

Hope this helps!