Module example.com/retract/self/prev is a module that retracts its own
latest version, as well as an earlier version.

A previous unretracted release version, v1.1.0, is still available.

-- .mod --
module example.com/retract/self/prev

go 1.15

retract v1.0.0-bad // bad
retract v1.9.0 // self

-- .info --
{"Version":"v1.9.0"}

-- p.go --
package p