For more content like this, buy my in-progress eBook, Data Serialization in Go⁠, and get updates immediately as they are added! The content in this post is included in my in-progress eBook, Data Serialization in Go, available on LeanPub. I’ve done a lot of JSON handling in Go. In the process, I’ve learned a number of tricks to solve specific problems. But one pattern in particular I find myself repeating ad infinitum.

How can you embed a struct with a custom MarshalJSON() method?

How can you marshal and unmarshal JSON array as though it were a struct in Go?

For more content like this, buy my in-progress eBook, Data Serialization in Go⁠, and get updates immediately as they are added! Have you ever found yourself writing a custom JSON marshaler in Go, because you needed something only slightly different than what the standard JSON marshaler provides? Maybe the consumer of your JSON payload expects an array where you have a single item. Or maybe you need to nest your object one level deeper in your JSON than is used in your application.

Go’s interfaces and “duck typing” makes it very easy to create simple mock or stub implementations of a dependency for testing. This has not dissuaded a number of people from writing generalized mocking libraries such as gomock and testify/mock, among others. Here I want to describe a simple alternative pattern I frequently use when writing tests for an interface, that I think is generally applicable to many use cases. No Silver Bullet Of course neither this approach, nor any other, is a one-size-fits-all solution.