Can you explain how a library for dependency injection could improve a Go standard library like net/http, io, encoding/json, or database/sql?
DI is also great for creating modular code you compose, instead of monoliths. It encourages the use of interfaces and information hiding - you should look into it, it's a very powerful technique.
Instead of asking how it would improve an arbitrary library, ask yourself "how screwed am I if 100% of the API surface for this library changes tomorrow?" Dependency injection would help you out of that faster that rewriting everything.