code: func GetCallObject(n ast.Node, ctx *Context) (*ast.CallExpr, types.Object) {
  	switch node := n.(type) {
  	case *ast.CallExpr:
  		switch fn := node.Fun.(type) {
  		case *ast.Ident:
  			return node, ctx.Info.Uses[fn]
  		case *ast.SelectorExpr:
  			return node, ctx.Info.Uses[fn.Sel]
  		}
  	}
  	return nil, nil
  }
docs: // GetCallObject returns the object and call expression and associated
  // object for a given AST node. nil, nil will be returned if the
  // object cannot be resolved.