Go For Fun: Sequence Breaking using For

Fri, 13 Oct 2023 15:50:00 -0500

Using early return is a well-known Go programming language trait.

A function must return early, as soon as possible, whenever it encounters errors. That way, there is only one possible happy path: reaching the end of the function. Thus, if you have multiple ways of achieving that happy path, it is recommended to break it apart into two different functions.

Consider this example snippet:

go
func DoSequence(input Input) (result string, err error) {
 // Do A
 if input.FieldA == "nothing" {
 return "", errors.New("Error A")
 }
 // Do B
 if input.FieldB == "nothing" {
 return "", errors.New("Error B")
 }
 // Do C
 if input.FieldC == "nothing" {
 return "", errors.New("Error C")
 }
 // All done!
 return "success", nil
}

In the above snippet, whenever the execution reaches a failure condition (the if statement for each Do A, Do B, etc), it returns early by sending the error message. So, the result is only accessible if we pass all these early returns. As you can see, this gets very verbose quickly. But people like them because the execution order is flat and linear.

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Go For Fun: Sequence Breaking using For