gogo-context

Golang, will context.TODO ever give error

ctx = context.TODO()
cmd := exec.CommandContext(ctx, <some_cmd>, <some_arg>)
fmt.Println(ctx.Err())

Is ctx.Err() is ever going to non-nil with ctx being context.TODO()?

Solution

  • context.TODO().Err() will always return nil, as can be easily seen in the source code:

    package context

// An emptyCtx is never canceled, has no values, and has no deadline.
type emptyCtx int

func (*emptyCtx) Err() error {
    return nil
}

// ...

var (
    todo       = new(emptyCtx)
)

// ...

// 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
}