You're developing a package in Go that interacts with multiple external libraries. Which feature would you use to handle different types returned by these libraries in a flexible way?

In Go, one way to handle different types returned by external libraries in a flexible manner is through interface polymorphism. By defining interfaces that capture the common behaviors needed from these different types, you can implement methods that operate on these interfaces. This allows you to work with various types through a unified interface without needing to know their concrete types at compile time. Struct embedding is used to compose types within a struct, but it doesn't directly address handling different types flexibly. Type assertion and type switch provide ways to determine the underlying types of variables but don't inherently provide a mechanism for handling different types in a flexible manner.