enhance: [GoSDK] Remove example in main pkg to make ut script work (#…

…37472)

Related to #31293

Example with main func/package causes `go list` command failed with vcs
error. This PR removes example files with main package. The example
snippet shall be added back in runnable test format.

---------

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

client/column/columns_test.go

@@ -40,9 +40,9 @@ func TestIDColumns(t *testing.T) {
 
 	t.Run("nil id", func(t *testing.T) {
 		_, err := IDColumns(intPKCol, nil, 0, -1)
-		assert.Error(t, err)
+		assert.NoError(t, err)
 		_, err = IDColumns(strPKCol, nil, 0, -1)
-		assert.Error(t, err)
+		assert.NoError(t, err)
 
 		idField := &schemapb.IDs{}
 		col, err := IDColumns(intPKCol, idField, 0, -1)