Travis on Window failed: "The process cannot access the file because it is being used by another process"

[shantuo]

https://travis-ci.com/google/wire/jobs/201184169

    --- FAIL: TestWire/ValueChain (0.56s)
        wire_test.go:110: go [list -f {{context.GOARCH}} {{context.Compiler}} -tags=wireinject -- unsafe]: exit status 1: go: open C:\Users\travis\AppData\Local\Temp\wire_test023669613\src\example.com\go.mod: The process cannot access the file because it is being used by another process.

[vangent]

That generally means that we opened the file but did not close it.