==========================================
parses function calls
==========================================
package main

func main() {
    println("1", 2)
    println()
}
---
(program
    (package_directive (package_name))
    (func_declaration (var_name) (block_statement
        (expression_statement (call_expression (var_name) (string) (number)))
        (expression_statement (call_expression (var_name))))))

============================================
parses selector expressions
============================================
package main

func main() {
    x.SomeMethod(x.SomeField, x.OtherField.NestedField);
}
---
(program
    (package_directive (package_name))
    (func_declaration (var_name) (block_statement
        (expression_statement (call_expression
            (selector_expression (var_name) (var_name))
            (selector_expression (var_name) (var_name))
            (selector_expression (selector_expression (var_name) (var_name)) (var_name)))))))

