Golang Field Alignment and structure size optimization

Since you're here already, I suppose you code in Golang and you're googling for a solution for a linter error mentioned in the article's title.

I won't go into detail when it comes to a memory management and field alignement in Go, because that's not the subject of this post. You can read more on that in Golang Field Alignment article.

Let's consider having a structs like this:

// Valid struct.
type Address struct {
    Name    string
    Street  string
    ZipCode string
    City    string
}

// Struct with misaligned fields.
type User struct {
    ID      int
    Name    string
    Address Address
}

Address contains all fields aligned, while the User struct not. What happens next?

Problem

When running a linter on your codebase, you can get errors that looks similarly to this:

golangci-lint run ./...
fieldalignment.go:3:11: fieldalignment: struct with 80 pointer bytes could be 72 (govet)
type User struct {
          ^

Long story short is that your struct's fields are in the wrong order and are using more memory than they could (again, see Golang Field Alignment).

Solution

Trying to manually fix the struct's fields order might be a pain if there're more than two.

As a solution we have a tool for that - fieldalignment. All you need to do is to install the fieldalignment tool:

go install golang.org/x/tools/go/analysis/passes/fieldalignment/cmd/fieldalignment@latest

And fix the code:

~/go/bin/fieldalignment -fix PATH

fieldalignment command does all the changes by itself. We end up with aligned fields in our struct, which now looks like this:

// Struct with aligned fields.
type User struct {
    Address Address
    Name    string
    ID      int
}

Now you can run the linter once again and focus on other issues :P

Sources

If you eager for more information, pls check:

• Golang Field Alignment

• Examine Go source code

• Run linters from Go code