Mastering Context Usage in Go: A Comprehensive Guide

Introduction

In everyday development, the use of context is inevitable. For instance, when working with packages like mongodb-driver, the Find method is commonly employed:

func (coll *Collection) Find(ctx context.Context, filter interface{}, opts ...*options.FindOptions) (cur *Cursor, err error) {
  // Implementation...
}

While it’s common to use context.Background(), the question arises: why might one use context.TODO() in this context? Let's delve into the differences between context.Background() and context.TODO().

Differences Between context.Background() and context.TODO()

Let’s examine their code implementations; essentially, they are identical.

var (
  background = new(emptyCtx)
  todo       = new(emptyCtx)
)
​
// Background returns a non-nil, empty Context. It is never canceled, has no values,
// and has no deadline. It is typically used by the main function, initialization, 
// and tests, and as the top-level Context for incoming requests.
func Background() Context {
  return background
}
​
// TODO returns a non-nil, empty Context. Code should use context.TODO when it's 
// unclear which Context to use or it is not yet available (because the surrounding 
// function has not yet been extended to accept a Context parameter).
func TODO() Context {
  return todo
}

From the comments, we gather that both context.Background() and context.TODO() are used to create a…