Avoid Using `init()` in Go Unless Necessary

The init() function in Go is a special function that gets executed automatically before the main() function, and even before any other code in the package. While it can be useful, overusing it can make your code harder to follow and maintain. Here’s why you should avoid using init() unless absolutely necessary.

Why `init()` Can Be Problematic

Hidden Logic: Since init() is executed automatically, it can introduce hidden behavior that isn't obvious from the code's main flow. This can make debugging and understanding the code more challenging, especially for larger projects.
Order of Execution: Go doesn't guarantee the order of execution of init() functions across different packages. If multiple packages have init() functions, it can lead to unpredictable behavior, making the program harder to reason about.
Complicated Testing: If important setup logic is hidden inside init(), it can be difficult to mock or bypass during testing. This can lead to tightly coupled tests that are harder to write and maintain.

When to Use `init()`

Despite the potential downsides, there are legitimate use cases for init():

Package-Level Configuration: If a package needs to initialize some state or configuration before being used (e.g., setting up a global logger), init() can be useful. However, make sure this setup is essential and cannot be handled in main() or elsewhere.
Registering Components: Some packages, especially those that provide extensible functionality like plugins or middleware, use init() to register components. This is acceptable, but try to document this behavior clearly to avoid confusion.

Example of `init()` Use

package main

import ( "log" "os" )

func init() { // Set up a global logger log.SetOutput(os.Stdout) log.Println("Logger initialized") }

func main() { log.Println("This is the main function") }

In this example, init() is used to set up a global logger before the main() function runs. While this is a valid use case, consider whether this setup could be done explicitly in main() for better clarity.

Further reading: https://www.digitalocean.com/community/tutorials/understanding-init-in-go