This assumes that the myapp author has either included all possible database/sql drivers, or that it provides a file for each database/sql driver with its own tag. Even just with SQL drivers (https://github.com/golang/go/wiki/SQLDrivers lists more than 20) this becomes hard quickly: imagine what could happen with application modules or plugins. Moreover, if the myapp maintainer doesn't want to import a specific package, you need to patch manually every time you build/run.

Sure, the current state is not unbearable... it just feels like an unneeded hop to jump through.

The fact that the use of something should be minimized doesn't imply that that something is not useful if used properly. I'm not advocating abuse of the feature I'm proposing; I'm advocating that it would be useful in certain limited scenarios - similarly to build tags, the -X flag to go tool link and cgo (all things that make reproducing an exact build basically impossible).

This request is missing a key detail: when would the package initializers for the extra packages run? (Before the initializers for the packages imported from package main, or after?)

At the moment, we have the nice property that package initializers run in a strict topological order.

Note that you can structure something more-or-less as @minux suggests using modules and replace directives.

example.com/main/go.mod:

module example.com/main

require example.com/inject v1.0.0

example.com/main/main.go:

package main

import _ "example.com/inject"
[…]

example.com/inject/go.mod

module example.com/inject
[…]

example.com/inject/inject.go:

package inject

import _ "github.com/go-sql-driver/mysql"

my.localhost/go.mod:

module my.localhost

require example.com/main v1.0.0

replace example.com/inject => ./inject

my.localhost/inject/go.mod:

module example.com/inject
[…]

my.localhost/inject/inject.go:

package inject

import _ "my.localhost/sql-driver"

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)