import stmt removed in output (sometimes)

[XiaochenCui]

I have some imports like:

import (
	"fmt"
	"environment/types"
	"environment/utils"
)

But those stmt disappeared from output (sometimes) even if the semantics of my code is completely vaild

[XiaochenCui]

What's the rule/pattern behind the import, and how can I avoid imports disappeared?

[XiaochenCui]

It doesn't help to add "github.com/stretchr/gogen/generic" to source file's imports