Response you are getting is in object form i.e.
{
"dstOffset" : 3600,
"rawOffset" : 36000,
"status" : "OK",
"timeZoneId" : "Australia/Hobart",
"timeZoneName" : "Australian Eastern Daylight Time"
}
Replace below line of code :
List<Post> postsList = Arrays.asList(gson.fromJson(reader,Post.class))
with
Post post = gson.fromJson(reader, Post.class);