wire.go file

[bereyes]

Sorry , I have a question:
wire.go file must be on main package? If I have wire.go in another package , when I use wire cmd I am getting "undeclared name: methodName" message, and I am not sure why.
EDIT:
If wire.go is in the same folder that a provider it fails:
Example

func InitializeWebAPI() *Container {
	wire.Build(
		NewControllerContainer,
		api.NewPingController,
	)
	return &Container{}
}

If wire.go is out that folder wire cmd is able to generate wire_gen.go , is it a correct behavior?
When my code looks like:

package infrastructure

import (
	"github.com/google/wire"
	"github.com/yyy/xxx-api-rules-test/cmd/entrypoint/api"
	"github.com/yyy/xxx-test/cmd/infrastructure/dependency"
)

func InitializeWebAPI() *dependency.Container {
	wire.Build(
		dependency.NewControllerContainer,
		api.NewPingController,
	)
	return &dependency.Container{}
}

wire works well
Could you help me please?

Thanks in advance